RESUMEN
In nuclear accident consequence assessment, dose contributions from radionuclide deposition on the human body have in the past generally been either ignored or estimated on the basis of rather simple models. Recent experimental work has improved the state of knowledge of relevant processes and parameter ranges. The results presented in this paper represent a first approach to a detailed assessment of doses from radiopollutant deposition on the human body, based on contaminant-specific data. Both the dose to skin from beta-emitters and the whole-body dose from gamma-emitters on body surfaces were found to give potentially significant contributions to dose. Further, skin penetration of some contaminants could lead to significant internal doses.
Asunto(s)
Contaminantes Radiactivos del Aire , Modelos Teóricos , Liberación de Radiactividad Peligrosa , Radiometría , Partículas beta , Rayos gamma , Humanos , Piel/efectos de la radiaciónRESUMEN
An isocratic high-performance liquid chromatography method has been developed for the quantification of the skin sensitisers trans-cinnamaldehyde and trans-cinnamic alcohol, and their cinnamic metabolites. The relative standard deviations (RSDs) between the gradients of eight sets of standard curves were 2.8, 3.1 and 1.9% for cinnamic alcohol, cinnamaldehyde and cinnamic acid, respectively. Sample analytes were derived from two series of experiments: in vitro full-thickness human skin absorption and metabolism studies and metabolism studies using human skin homogenates, with non-radiolabelled cinnamic compounds. Skin absorption and metabolism experiments were performed in the absence and presence of the alcohol dehydrogenase inhibitor, pyrazole. Samples from full-thickness skin absorption studies were analysed without extraction; cinnamic compounds from within skin were extracted into methanolic solutions using newly developed methods. The intra-assay RSDs ranged from 0.17 to 2.52% for cinnamic alcohol, 0.24 to 9.14% for cinnamaldehyde and 0.26 to 6.43% for cinnamic acid. The inter-assay RSDs for cinnamic alcohol, cinnamaldehyde and cinnamic acid, respectively, as determined from n=20 HPLC runs, were 2.10, 4.16 and 2.26%.
Asunto(s)
Acroleína/análogos & derivados , Acroleína/análisis , Cromatografía Líquida de Alta Presión/métodos , Propanoles/análisis , Absorción Cutánea , Acroleína/farmacocinética , Adulto , Humanos , Persona de Mediana Edad , Propanoles/farmacocinética , Reproducibilidad de los Resultados , Espectrofotometría UltravioletaRESUMEN
The aim of this study was to evaluate the use of an in vitro skin diffusion cell system as a model for assessing decontaminants against the chemical warfare agent sulphur mustard (SM). The in vitro absorption rates of SM through heat-separated human (157 +/- 66 microg cm(-2) h(-1)) and pig-ear (411 +/- 175 microg cm(-2) h(-1)) epidermal membranes were in agreement with previous in vivo studies that quoted skin absorption rates of 150 and 366 microg cm(-2) h(-1), respectively. Decontaminants (fuller's earth, Ambergard and BDH spillage granules) were ranked in order of effectiveness by measuring the skin absorption rates and the percentage of applied dose of SM that penetrated human and pig-ear epidermal membranes. The effectiveness of fuller's earth measured in this in vitro study using human epidermal membranes was in agreement with a previous in vivo human volunteer study. Similarly, the effectiveness of fuller's earth and Ambergard measured in vitro with pig-ear epidermal membranes was in agreement with a previous in vivo study conducted on rats. However, there was complete disparity in the ranking of decontaminants between human and pig-ear epidermal membranes measured in vitro. Thus, although pig-ear skin may be a relatively good model for predicting the human skin absorption of SM, it is a poor model for testing decontamination systems. The results of this study further validate the use of Franz-type glass diffusion cells containing human epidermal membranes as a model for predicting in vivo human skin absorption.
Asunto(s)
Oído Externo/metabolismo , Epidermis/metabolismo , Gas Mostaza/farmacocinética , Absorción Cutánea/fisiología , Compuestos de Aluminio/farmacocinética , Compuestos de Aluminio/uso terapéutico , Animales , Autorradiografía , Descontaminación/métodos , Relación Dosis-Respuesta a Droga , Etanol/química , Humanos , Técnicas In Vitro , Compuestos de Magnesio/farmacocinética , Compuestos de Magnesio/uso terapéutico , Membranas , Gas Mostaza/toxicidad , Silicatos/farmacocinética , Silicatos/uso terapéutico , Solubilidad , Solventes/química , Especificidad de la Especie , Porcinos , Factores de Tiempo , Agua/químicaRESUMEN
A selection of 17 aldehydes (13 sensitizing and 4 non-sensitizing), all of which possessed a benzene ring, were evaluated using structure-activity relationships (SARs). The sensitizing compounds were classified as strong, moderate or weak skin sensitizers on the basis of in vivo data. The aldehydes were grouped into 4 distinct subcategories of functionally related aldehydes that were termed aryl-substituted aliphatic, aryl, aryl with special features (that can undergo metabolism) and alpha,beta-unsaturated aldehydes. It was observed that a structure-activity relationship could be derived for a subset of aldehydes that could react via the same chemical mechanism. This further supports the view that applying knowledge on reaction mechanisms to develop SAR models can provide a more accurate means of investigating and predicting the sensitization potential of structurally and functionally related chemicals.
Asunto(s)
Aldehídos/química , Aldehídos/efectos adversos , Animales , Dermatitis Alérgica por Contacto/etiología , Relación Estructura-ActividadRESUMEN
New therapeutic compounds intended for use on the skin or for delivery through application to the skin and agrochemicals, whose use may result in skin exposure, must be tested for bioavailability as the result of absorption. This unit contains a protocol for measuring skin absorption in vitro using the diffusion cell skin absorption method (SAM), which can be used to measure percutaneous absorption after topical application. Usually a radiolabeled compound is used, but if a suitable specific assay is available, nonradioactive compounds may be tested. The procedure is applicable to skin from a variety of species.
Asunto(s)
Disponibilidad Biológica , Absorción Cutánea , Piel/metabolismo , Toxicología/métodos , Administración Cutánea , Agroquímicos/farmacocinética , Alternativas a las Pruebas en Animales , Animales , Humanos , Modelos Biológicos , Preparaciones Farmacéuticas/administración & dosificación , Preparaciones Farmacéuticas/metabolismo , Manejo de Especímenes/métodos , Manejo de Especímenes/normas , Técnicas de Cultivo de Tejidos/instrumentación , Técnicas de Cultivo de Tejidos/métodos , Técnicas de Cultivo de Tejidos/normas , Toxicología/instrumentación , Toxicología/normasRESUMEN
trans-Cinnamaldehyde and trans-cinnamic alcohol have been commonly reported to cause allergic contact dermatitis (ACD) in humans. Cinnamaldehyde is a more potent skin sensitizer than cinnamic alcohol. It has been hypothesized that cinnamic alcohol is a "prohapten" that requires metabolic activation, presumably by oxidoreductase enzymes such as alcohol dehydrogenase (ADH) or cytochrome P450 2E1 (CYP2E1), to the protein-reactive cinnamaldehyde (a hapten). In this study, the in vitro percutaneous absorption and metabolism of cinnamaldehyde and cinnamic alcohol (78 micromol dose) has been examined using freshly excised, metabolically viable, full-thickness breast and abdomen skin from six female donors. Penetration rates and total cumulative recoveries of cinnamic compounds that were present in receptor fluid, extracted from within the skin, evaporated from the skin surface, or remained unabsorbed on the skin surface after 24 h were quantified by reversed-phase high-performance liquid chromatography. Biotransformation of cinnamaldehyde to both cinnamic alcohol and cinnamic acid was observed. Topically applied cinnamic alcohol was converted to cinnamaldehyde (found on the skin surface only) and cinnamic acid. To establish whether these biotransformations were enzymatic, experiments were performed in the absence and presence of varying concentrations (80-320 micromol) of the ADH/CYP2E1 inhibitors pyrazole or 4-methylpyrazole. The observation that pyrazole significantly reduced (p < 0.05) the total penetration of cinnamic metabolites into receptor fluid, following either cinnamaldehyde or cinnamic alcohol treatment, but did not significantly affect parent chemical penetration, suggests that we are measuring cutaneous metabolic products of ADH activity. The skin absorption and metabolism of cinnamaldehyde and cinnamic alcohol will play an important role in the manifestation of ACD following topical exposure to these compounds.
Asunto(s)
Acroleína/análogos & derivados , Alérgenos/metabolismo , Dermatitis Alérgica por Contacto , Propanoles/farmacocinética , Absorción Cutánea/fisiología , Acroleína/farmacocinética , Adulto , Biotransformación , Cromatografía Líquida de Alta Presión , Femenino , Humanos , Técnicas In Vitro , Persona de Mediana Edad , Pirazoles/farmacologíaRESUMEN
Percutaneous absorption of pesticides is a major determinant for risk assessment. Furthermore, cutaneous metabolism plays a role in penetration of certain chemicals. Therefore, the aim of these studies was to determine the transdermal metabolism of three related compounds [the herbicide, fluroxypyr methylheptyl ester (FPMH), fluroxypyr methyl ester (FPM), and fluroxypyr (FP)] during penetration through human and rat skin in vitro. The data presented in this article show that both FPM and FPMH were completely metabolized during their passage through human and rat skin in vitro. The only metabolite produced was that of the hydrolysis product, FP, with no parent ester penetrating through the skin. The extent of FP formation within the skin was directly correlated to the degree of stratum corneum reservoir formation. The larger the stratum corneum reservoir, the lower the levels of FP recovered from within the skin. This suggests that as the ester partitioned out of the SC it was immediately hydrolyzed to FP, which could then pass freely through the remainder of the epidermis and dermis. Similar metabolic profiles were observed for the transdermal metabolism of FPM and FPMH in previously frozen rat skin, indicating the robust nature of the esterase enzymes involved. In conclusion, systemic exposure after skin contact with FPM or FPMH is likely to be to the acid metabolite, FP, only and not to the parent ester. In addition, the rate and extent of percutaneous absorption will be a major determinant of cutaneous metabolism.
Asunto(s)
Glicolatos/farmacocinética , Herbicidas/farmacocinética , Absorción Cutánea , Animales , Glicolatos/química , Herbicidas/química , Humanos , Masculino , Ratas , Ratas Endogámicas F344RESUMEN
Fluroxypyr methyl ester (FPM) and the herbicide fluroxypyr methylheptyl ester (FPMH) are completely hydrolyzed during penetration through human and rat skin in vitro to the acid metabolite, fluroxypyr (FP) (). This article presents additional studies to determine the enzyme kinetics (K(m) and V(max)) of this ester hydrolysis, using crude rat whole-skin homogenate. Both FPM and FPMH were extensively metabolized in rat skin homogenates to the acid metabolite, FP. In no instance were any other metabolites detected. FPM was essentially hydrolyzed completely within 1 h. In FPMH incubations, there was still parent ester present after 24 h at all concentrations tested. The kinetics of hydrolysis of the two esters were different: V(max) was approximately 3-fold greater for FPM than FPMH (1400 and 490 micromol FP/min/g of tissue, respectively); however, K(m) values were very similar, 251 and 256 microM, respectively. Preliminary inhibitory studies suggest that FPM and FPMH are hydrolyzed by a carboxylesterase, because this reaction was inhibited by bis-p-nitrophenyl phosphate. Mercuric chloride (an inhibitor of A-esterase and arylesterase) and eserine (a cholinesterase inhibitor) had no inhibitory effect on the hydrolysis of FPM or FPMH. Taken together with the data presented by, it can be concluded that no parent ester will pass through the skin in vivo, only the metabolite, FP. Therefore, first pass metabolism will be complete before these compounds reach the systemic circulation.
Asunto(s)
Glicolatos/farmacocinética , Herbicidas/farmacocinética , Piel/metabolismo , Animales , Esterasas/metabolismo , Glicolatos/química , Herbicidas/química , Hidrólisis , Masculino , Ratas , Ratas Endogámicas F344 , Piel/enzimologíaRESUMEN
The purpose of this study was to measure the absorption and intra-epidermal fate of 35S-radiolabelled sulphur mustard (35SM) in human breast skin in vitro. Skin (full-thickness or heat-separated epidermis) was placed into static diffusion cells and was exposed to droplets of liquid 35SM or saturated 35SM vapour. Amounts of 35SM penetrating the skin were measured from which skin absorption rates were calculated. Unbound radiolabel was washed from the surface, extracted from the skin and analysed to determine the identity of the radiolabelled species in order to measure the extent of hydrolysis of sulphur mustard. Penetration rates of liquid 35SM measured in vitro (71-294 microg cm(-2) h(-1)) were in agreement with those measured previously in vivo using human volunteers (60-240 microg cm(-2) h(-1)). Rates of liquid 35SM skin absorption under occluded, infinite dose conditions were highest through heat-separated epidermal membranes (294+/-58 microg cm(-2) h(-1)) and lowest through full-thickness skin (71+/-14 microg cm(-2) h(-1)). Fluxes of saturated 35SM vapour (110+/-75 microg cm(-2) h(-1)) through heat-separated membranes were similar to those previously measured through human forearm skin in vivo (162 microg cm(-2) h(-1)). Although hydrolysis of 35SM did occur, both on the surface and within the skin, it accounted for only a small percentage of the total applied dose (<2.7+/-1.2%). The difference in total amount of liquid 35SM penetrated between occluded and unoccluded conditions in vitro (79+/-14%) was similar to that lost as vapour from unoccluded skin in vivo (80%). A substantial reservoir of 35SM (14-36% of the applied dose) was measured within heat-separated epidermal membranes for up to 24 h which may have significant implications for the management of personnel exposed to sulphur mustard.
Asunto(s)
Gas Mostaza/farmacocinética , Autorradiografía , Difusión , Femenino , Humanos , Hidrólisis , Técnicas In Vitro , Membranas/metabolismo , Absorción Cutánea , Radioisótopos de AzufreRESUMEN
Chemical allergens that induce contact sensitivity cause changes in levels of epidermal cytokines. In mice one of the earliest epidermal cytokines to be upregulated following sensitization is interleukin-1 beta (Iota L-1 beta). The present study investigated the kinetics and in situ localization of induced IL-1 beta expression in mouse skin following topical exposure to the contact allergen oxazolone. Mice were exposed topically to 1% oxazolone, with control mice exposed to vehicle (acetone:olive oil 4:1) alone, and at various times thereafter skin was excised for IL-1 beta mRNA and protein determination by in situ hybridization and enzyme-linked immunosorbant assay (ELISA), respectively. IL-1 beta mRNA was found to be expressed constitutively at low levels in skin from naïve (untreated) and vehicle-treated mice, with mRNA localized in some hair follicles and sebaceous glands; no IL-1 beta mRNA was detected in the epidermis of control animals. Following topical exposure of mice to oxazolone for 5-15 min, upregulation of IL-1 beta mRNA was observed in the epidermis, dermis, hair follicles, and sebaceous glands; at 90 min and beyond the pattern of IL-1 beta mRNA expression declined toward control. Analysis of whole skin homogenates by ELISA demonstrated cutaneous IL-1 beta protein to be present constitutively in both vehicle-treated and naïve mice. Following exposure to oxazolone, cutaneous IL-1 beta protein expression was elevated at 30 min, decreased at 1 h, and fell below the limit of detection of the assay at 2 h before returning to constitutive levels at 4 and 24 h. IL-1 beta protein levels in vehicle-treated mice, naïve mice, and mice treated with the respiratory allergen trimellitic anhydride were unchanged over this time period. The present study demonstrated that IL-1 beta mRNA expression was upregulated rapidly and transiently in well-defined regions of mouse epidermis and dermis during contact sensitization, and was succeeded by an elevation in IL-1 beta protein. This early highly localized upregulation of IL-1 beta lends further support to the hypothesis that this cytokine plays a key role in the initial stages of skin sensitization. Such information will enhance our understanding of the molecular processes involved in allergic contact dermatitis and may provide a mechanistic basis for designing refined animal and in vitro alternatives to existing models of skin sensitization.
Asunto(s)
Dermatitis por Contacto/inmunología , Interleucina-1/genética , ARN Mensajero/análisis , Piel/metabolismo , Animales , Femenino , Interleucina-1/biosíntesis , Ratones , Ratones Endogámicos BALB C , Oxazolona/toxicidadRESUMEN
Alcohol dehydrogenase (ADH; EC 1.1.1.1) and aldehyde dehydrogenase (ALDH; EC 1.2.1.3.) are important enzymes involved in the biotransformation of both alcohols and aldehydes. Today, six classes of ADH and twelve classes of ALDH have been defined in mammals. Here we report the detection and localisation of three classes of ADH and two classes of ALDH in human skin, using Western blot analysis and immunohistochemistry with class-specific antisera. Western blot analysis of human skin cytosol revealed that class I-III ADH and class 1 and class 3 ALDH enzymes are expressed, constitutively, in three different anatomical regions of human skin (foreskin, breast, abdomen). Densitometric analysis of the immunoreactive bands revealed differential constitutive expression of these enzymes in foreskin, breast, and abdomen skin. Immunohistochemistry showed the presence of class I ADH and class III ADH enzymes, predominantly in the epidermis with some localised expression in the dermal appendages of human skin. In comparison, staining for class II ADH was more faint in the epidermis with very little dermal expression. Class 1 ALDH and class 3 ALDH were predominantly localised to the epidermis with minimal, highly localised dermal appendageal expression. These cutaneous ADH and ALDH enzymes may play significant roles in the metabolism of endogenous or xenobiotic alcohols and aldehydes.
Asunto(s)
Alcohol Deshidrogenasa/análisis , Aldehído Deshidrogenasa/análisis , Piel/enzimología , Adolescente , Adulto , Anciano , Alcohol Deshidrogenasa/clasificación , Aldehído Deshidrogenasa/clasificación , Western Blotting , Niño , Preescolar , Citosol/enzimología , Dermis/enzimología , Epidermis/enzimología , Femenino , Humanos , Inmunohistoquímica , Lactante , Masculino , Persona de Mediana Edad , Peso MolecularRESUMEN
The induction of contact sensitization and other cutaneous immune responses is dependent upon the activity of epidermal cytokines. One such, keratinocyte-derived tumour necrosis factor alpha (TNF-alpha), is thought to provide the stimulus for the migration of Langerhans cells from the epidermis and their accumulation as immunocompetent dendritic cells in draining lymph nodes. In these investigations we have examined the stimulation by allergen of cutaneous TNF-alpha production and the induced epidermal expression of mRNA for TNF-alpha. Topical exposure of mice to oxazolone, a skin-sensitizing chemical, resulted in cutaneous TNF-alpha protein production that was maximal 2-h following treatment and then declined markedly. The same treatment resulted in highly localized and transient expression of epidermal TNF-alpha mRNA as judged by in situ hybridization. Epidermal mRNA for TNF-alpha was apparent 10 min following exposure to oxazolone, but was no longer detectable at 20 min. A similar pattern of TNF-alpha mRNA expression in the epidermis was provoked by intradermal exposure to interleukin 1 beta, a cytokine shown previously to induce TNF-alpha. Such rigorous regulation of temporal and spatial expression was shown not to be a characteristic of all epidermal cytokines induced by chemical allergen. Exposure to oxazolone under the same conditions resulted in a more widespread and more persistent expression of epidermal mRNA for interleukin 6. These data demonstrate that during skin sensitization the induced expression of epidermal TNF-alpha is finely controlled in space and time. It is proposed that such regulation facilitates the initiation of cutaneous immune responses while preventing excessive inflammation that would result from more persistent TNF-alpha production.
Asunto(s)
Interleucina-6/biosíntesis , Piel/inmunología , Factor de Necrosis Tumoral alfa/biosíntesis , Adyuvantes Inmunológicos/farmacología , Animales , Dermatitis Alérgica por Contacto/inmunología , Regulación de la Expresión Génica , Hibridación in Situ , Interleucina-1/farmacología , Interleucina-6/genética , Ratones , Oxazolona/farmacología , Piel/efectos de los fármacos , Factor de Necrosis Tumoral alfa/genéticaRESUMEN
The in vitro percutaneous absorption and skin metabolism of coumarin (1,2-benzopyrone) was studied in metabolically viable human, rat (F344), and mouse (CD1 and DBA/2) skin. Following application of [14C]coumarin (3.7 microg/cm2; 0.02% in ethanol) to unoccluded skin in flow-through diffusion cells of a skin absorption model (SAM), the absorption through the skin into the receptor fluid at 72 hr was rapid and extensive in all species, reaching (mean +/- SD) 50.4 + 9.1% of the applied dose in human, 51.3 +/- 7.3% in rat, and 44.9 +/- 13.5% in mouse. When the skin was occluded immediately after exposure, the extent of absorption at 72 hr was enhanced in all species. At 72 hr, substantial amounts of [14C]coumarin were found in unoccluded mouse skin (31.7 +/- 13.6%), with less in human (10.2 +/- 6.5%) and rat (12.7 +/- 5.0%) tissue. When occluded, the skin residues at 72 hr were 10.4 +/- 11.7% (mouse), 8.5 +/- 3.9% (human), and 11.9 +/- 7.5% (rat). The absorption of coumarin through rat skin into the receptor fluid over 72 hr was linearly related to the applied dose (r2 = 0.998 unoccluded skin; r2 = 0.999 occluded skin) over the dose range 3.7 to 378.7 microg/cm2. The nature and extent of cutaneous metabolism was studied following (i) topical application for 24 hr to human, rat, and mouse skin in the SAM system; (ii) incubation at 37 degrees C for up to 6 hr with human, rat, and mouse whole skin homogenates; and (iii) incubation at 37 degrees C for up to 24 hr with freshly isolated and cultured human epidermal keratinocytes. HPLC and GCMS analyses of skin extracts and receptor fluid confirmed that, in all three species, only the parent compound, coumarin, was present at all times from 10 min to 24 hr. These data indicate that topically applied coumarin is rapidly and extensively absorbed through human, rat, and mouse skin, and that the compound remains metabolically unchanged during absorption. These observations may have implications for the safe and effective use of coumarin in consumer products which come into contact with the skin and as a topical therapeutic agent.
Asunto(s)
Antineoplásicos/farmacocinética , Cumarinas/farmacocinética , Absorción Cutánea , Anciano , Animales , Antineoplásicos/metabolismo , Antineoplásicos/toxicidad , Mama , Radioisótopos de Carbono , Células Cultivadas , Cromatografía Líquida de Alta Presión , Cumarinas/metabolismo , Cumarinas/toxicidad , Difusión , Células Epidérmicas , Epidermis/efectos de los fármacos , Epidermis/metabolismo , Femenino , Cromatografía de Gases y Espectrometría de Masas , Humanos , Marcaje Isotópico , Queratinocitos/citología , Queratinocitos/efectos de los fármacos , Queratinocitos/metabolismo , Masculino , Ratones , Ratones Endogámicos DBA , Persona de Mediana Edad , Ratas , Ratas Endogámicas F344 , Absorción Cutánea/efectos de los fármacos , Absorción Cutánea/fisiología , Especificidad de la EspecieRESUMEN
Glycine conjugation is an important route of metabolism and detoxication of carboxylic acids in the liver. In this paper the in vitro cutaneous metabolism of [carboxyl-14C]benzoic acid to its glycine conjugate hippuric acid in rat and human skin is reported. Cutaneous glycine conjugation was studied in F344 rat and human epidermal keratinocytes using two systems: (1) freshly isolated keratinocytes in suspension and (2) primary keratinocyte cultures. For comparative purposes, studies were also carried out in freshly isolated and cultured F344 rat hepatocytes. After incubation of 5 x 10(6) cells with 1 microM benzoic acid at 37 degrees C for 8 hr, no glycine conjugation was observed in rat and human keratinocyte suspensions, with greater than 98% of the radioactivity recovered as the parent compound. In contrast, cultured keratinocytes exhibited glycine conjugation, with 10.9 +/- 1.0% (mean SEM, n = 3) and 2.1 +/- 0.6% (mean SEM, n = 3) conversion to hippuric acid at 8 hr in rat and human cells, respectively. Tissue-specific differences in metabolism were observed, with conjugation in hepatocytes significantly greater (P < 0.05) than in keratinocytes at all times up to 8 hr. After incubation of benzoic acid with cultured hepatocytes for 8 hr, more than 98% of the of the radioactivity was recovered as the glycine conjugate. These studies indicate that rat and human skin possesses low, but demonstrable, glycine-conjugating activity, and that keratinocytes in primary culture may provide a better system than freshly isolated cell suspensions for studying such activity.
Asunto(s)
Glicina/metabolismo , Queratinocitos/metabolismo , Piel/metabolismo , Adulto , Animales , Benzoatos/metabolismo , Ácido Benzoico , Células Cultivadas , Femenino , Humanos , Hígado/citología , Hígado/metabolismo , Masculino , Persona de Mediana Edad , Embarazo , Ratas , Ratas Endogámicas F344 , Piel/citología , Especificidad de la EspecieRESUMEN
4,4'-Methylenebis[2-chloroaniline] (MbOCA) and 4,4'-methylenedianiline (MDA) are widely used industrial chemicals classified as suspect human carcinogens. There is considerable occupational skin exposure to these compounds, and consequently, it is important to establish an efficient washing procedure after skin contamination. Four washing solutions were studied (100% ethanol, 100% water, 1 and 10% (v/v) aqueous soap) using fresh human and male F344 rat skin in flow-through diffusion cells. All solutions were equally effective at removing MbOCA and MDA from the surface of human skin, with 21-47% of the applied dose removed at 72 hr. In contrast, with rat skin 100% water and 1% soap solution were significantly less (p < 0.05) effective than 10% soap solution and 100% ethanol at removing MbOCA and MDA. Washing the skin surface at 3 or 30 min significantly reduced (p < 0.05) the absorption of MbOCA and MDA into and through human and rat skin at 72 hr by two- to threefold, compared with control unwashed skin. Washing the skin after this critical time point did not significantly reduce the absorption. These studies suggest that MbOCA and MDA are rapidly absorbed from the skin surface into the skin. Therefore, in order to reduce systemic exposure, the skin must be washed within the first 30 min after contamination has occurred. For human skin, the choice of washing solution employed was not as critical as the time of washing. This is in contrast to the rat, where the higher concentration soap and ethanol solutions were more effective for skin decontamination.
Asunto(s)
Compuestos de Anilina/farmacocinética , Descontaminación/métodos , Metilenobis (cloroanilina)/farmacocinética , Absorción Cutánea , Administración Tópica , Compuestos de Anilina/administración & dosificación , Animales , Cámaras de Difusión de Cultivos , Etanol , Humanos , Masculino , Metilenobis (cloroanilina)/administración & dosificación , Ratas , Jabones , Factores de TiempoRESUMEN
The comparative absorption of the fragrance and industrial compound, benzyl acetate, has been studied in rat and human skin, using shaved, full-thickness dorsal skin of male Fischer 344 rats and full-thickness human skin obtained from patients undergoing surgical resection. Penetration of the compound through rat and human skin was evaluated in vitro in flow-through diffusion cells following topical application of neat [methylene-14C] benzyl acetate (33.1 mg/cm2) to the epidermal surface and occlusion with a teflon cap, 2.9 cm above the skin surface. The absorption of benzyl acetate across rat skin was rapid and extensive, reaching 34.3 +/- 3.9% of the applied dose (11.3 +/- 1.3 mg/cm2) (mean +/- SD, n = 12) at 24 hr and 55.8 +/- 5.0% of the applied dose (18.5 +/- 1.7 mg/cm2) at 72 hr. The penetration of benzyl acetate was significantly (P < 0.05) less rapid and extensive through human skin, reaching 5.5 +/- 0.1% of the applied dose (1.8 +/- 0.0 mg/cm2) (mean +/- SD, n = 12) at 24 hr and 17.8 +/- 3.3% of the applied dose (5.9 +/- 1.1 mg/cm2) at 72 hr. The rate of penetration of benzyl acetate was greater through rat skin than through human tissue at all time points studied up to 72 hr. The maximum rate of skin penetration was 0.6 +/- 0.1 mg/cm2/hr and 0.1 +/- 0.0 mg/cm2/hr through rat and human skin, respectively. These data indicate that systemic exposure to benzyl acetate may occur after skin contact in humans. They also support the evidence from the literature that human skin is generally less permeable to xenobiotics than rat skin.
Asunto(s)
Compuestos de Bencilo/farmacocinética , Absorción Cutánea , Animales , Humanos , Técnicas In Vitro , Masculino , Ratas , Ratas Endogámicas F344 , Especificidad de la EspecieRESUMEN
The percutaneous absorption of the plasticizer and fragrance chemical diethyl phthalate (DEP) has been evaluated in vitro in flow-through diffusion cells using shaved full-thickness skin from male Fischer 344 rats and human breast skin. Neat DEP (16.3-20.6 mg/cm(2)) was applied to the epidermal surface of the skin, which was then either left uncovered (unoccluded) or covered (occluded) with a teflon cap 2.9 cm above the skin surface. The absorption of DEP through rat skin and into the receptor fluid was relatively extensive reaching 35.9 +/- 2.9% (mean +/- SD, n = 4) of the applied dose over 72 hr when the skin was occluded and 38.4 +/- 2.5% (mean +/- SD, n = 3) when the skin was unoccluded. Absorption of DEP through human skin was significantly less (P < 0.05) than through rat skin reaching 3.9 +/- 1.2% (mean +/- SD, n = 4) of the applied dose over 72 hr when the skin was occluded and 4.8 +/- 0.7% (mean +/- SD, n = 3) when the skin was unoccluded. Occlusion of the skin did not significantly alter the percutaneous absorption of DEP through rat or human skin. There was a four-fold variation in absorption between skin samples taken from human donors, ranging from 1.6 +/- 1.2% (mean +/- SD, n = 3) to 8.7 +/- 3.9% (mean +/- SD, n = 6) at 72 hr. This inter-individual variation was greater than the variation between animals, which ranged from 26.4 +/- 3.3% (mean +/- SD, n = 4) to 38.9 +/- 0.6% (mean +/- SD, n = 5). This information may be of significance for the safety evaluation of DEP for occupational and consumer use. Although human in vivo data are lacking, the percutaneous absorption of DEP through rat skin in vitro compares well with rat in vivo data from the literature, which supports the use of this technique as a model for in vivo absorption.
RESUMEN
The percutaneous absorption of 4'4'-methylene-bis(2-chloroaniline) (MbOCA) and 4,4'-methylenedianiline (MDA) has been investigated after topical application to full-thickness skin from male Fischer 344 rats and humans in flow-through diffusion cells, on four separate occasions. After application of MbOCA (13.4-62.5 mug/cm(2) in ethanol) to unoccluded skin, the extent of absorption into the receptor fluid at 72 hr was poor, reaching 1.3 +/- 0.6% and 2.4 +/- 1.4% (mean +/- SD, n = 10-12) of the applied dose, for rat and human skin, respectively. When the skin was occluded with a teflon cap, the absorption of MbOCA at 72 hr was not statistically significantly different through rat or human skin. After application of MDA (17.7-40.6 mug/cm(2) in ethanol) to unoccluded skin, the absorption into the receptor fluid at 72 hr was more extensive than for MbOCA, reaching 6.1 +/- 2.0% and 13.0 +/- 4.3% (mean +/- SD, n = 10-12) of the applied dose for rat and human skin, respectively. When the skin was occluded, the absorption of MDA at 72 hr was significantly enhanced (P<0.05), reaching 13.3 +/- 4.0% and 32.9 +/- 9.0% (mean +/- SD, n = 14-16), for rat and human skin, respectively. At the end of each experiment, considerable residual material remained within the skin for MbOCA (about 31-66%) and MDA (about 23-58%). The total recovery of radioactivity for all experiments was generally >/=90%. These data indicate that significant amounts of MbOCA and MDA are absorbed into rat and human skin in vitro although diffusion through the tissue into the receptor fluid is relatively low. If these in vitro observations are representative of events occurring under conditions of human exposure in vivo, they may have implications for the risk assessment of the chemicals for occupational use.
RESUMEN
The in vitro percutaneous absorption of three model compounds, nicotinic acid, phenol and benzoic acid, and the herbicide triclopyr butoxyethyl ester (triclopyr BEE) has been investigated in flow-through diffusion cells using skin from male Fischer 344 rats and humans. After the application of the four chemicals to the epidermal surface of unoccluded full-thickness rat skin, the absorption of each compound across the skin and into the receptor fluid at 72 hr reached 3.7 +/- 0.3, 5.7 +/- 0.6, 26.7 +/- 3.7 and 48.3 +/- 1.2% (mean +/- SD, n = 2-7) of the applied dose for triclopyr BEE, nicotinic acid, phenol and benzoic acid, respectively. After the application of the four chemicals to the epidermal surface of unoccluded full-thickness human skin, the absorption of each compound across the skin and into the receptor fluid at 72 hr was significantly (P < 0.05) less than through rat skin, reaching 0.7 +/- 0.1, 0.7 +/- 0.2, 18.8 +/- 1.3 and 37.8 +/- 6.9% (mean +/- SD, n = 2-7) of the applied dose for triclopyr BEE, nicotinic acid, phenol and benzoic acid, respectively. Occlusion of the skin surface with teflon caps often significantly (P < 0.05) enhanced the percutaneous absorption of the model compounds, although this effect was not uniform, varying with the compound under study and the skin (rat or human) used. When rat skin was occluded with teflon caps, the extent of absorption at 72 hr reached 8.6 +/- 0.8, 36.2 +/- 1.7 and 51.8 +/- 3.3% (mean +/- SD, n = 3-4) for nicotinic acid, phenol and benzoic acid, respectively. Corresponding values for human skin occluded with teflon caps were 3.3 +/- 1.6, 47.1 +/- 0.5 and 65.5 +/- 7.1% (mean +/- SD, n = 3-4). The experiments on the absorption of each model compound through rat and human skin were repeated and there was generally good agreement between the results from the two sets of experiments. The in vitro data reported compare favourably with data obtained by other workers using both in vitro and in vivo methodologies. The in vitro: in vivo correlation supports the use of the flow-through diffusion cell system as a model for the prediction of percutaneous absorption in vivo in the rat and in humans.
Asunto(s)
Benzoatos/farmacocinética , Glicolatos/farmacocinética , Niacina/farmacocinética , Fenoles/farmacocinética , Piel/metabolismo , Absorción , Animales , Benzoatos/administración & dosificación , Ácido Benzoico , Relación Dosis-Respuesta a Droga , Humanos , Cinética , Masculino , Fenol , Ratas , Ratas Endogámicas F344RESUMEN
The effect of vehicle and occlusion on the in vitro percutaneous absorption of [methylene-14C]-benzyl acetate (1.7-16.6 mg/cm2) has been studied in diffusion cells using full thickness skin from male Fischer 344 rats. Absorption of neat benzyl acetate through rat skin occluded with parafilm was 49.3 +/- 2.0% (mean +/- SD, n = 4) after 48 hr. When benzyl acetate in ethanol was applied to the skin and the skin was occluded with parafilm, the extent of absorption at 48 hr was not significantly different from that after neat application. However at 6 hr, as the ethanol content of the application mixture was increased, the absorption of benzyl acetate through occluded skin was enhanced proportionally (r = 0.999). When phenylethanol was used as a vehicle, the extent of the benzyl acetate absorption through occluded skin at 48 hr was enhanced (P less than 0.05) compared with that after application neat; with 50% (v/v) phenyl-ethanol, absorption at 48 hr was 56.3 +/- 4.9%. However, this enhanced absorption did not correlate with the proportion of phenylethanol in the application mixture. When dimethylsulphoxide was used as a vehicle, the extent of absorption of benzyl acetate through occluded skin at 48 hr was enhanced (P less than 0.05) compared with that after application neat (absorption was 59.3 +/- 3.7% of the applied dose when 50% (v/v) dimethylsulphoxide was used). As the dimethylsulphoxide content of the application mixture was increased, the absorption of benzyl acetate was enhanced proportionally. Occlusion of the skin surface with parafilm often significantly enhanced absorption (P less than 0.05), although the effect varied with time and vehicle. In general, the degree of any enhanced absorption caused by the use of a vehicle or occlusion of the skin was small, and, in most cases, would be unlikely to be toxicologically significant.