RESUMEN
In isolated hepatocytes, the environmental estrogen bisphenol A (BPA) is metabolized into a mono-glucuronide and a glucuronide/sulfate diconjugate. Little is known about the fate of the diconjugate in the liver. The present study focused on the metabolism and dispostion of BPA diconjugate in the liver using a perfusion method. In Sprague-Dawley rats, BPA (15,150 or 1,500 nmol) was applied into the liver. In male rats, the infused BPA was conjugated to both glucuronide and a diconjugate during passage through the liver. The diconjugate was observed at high-dose application of the substrate. In female rats, the chemical was conjugated almost exclusively to the glucuronide in all doses utilized in this study. In both the male and female rats, the resultant metabolites were preferentially excreted into the bile. These results suggest that BPA is conjugated primarily to mono-glucuronide in rat liver; and that in males, diconjugate production occurs under conditions of high-dose exposure to BPA.
Asunto(s)
Compuestos de Bencidrilo/análisis , Glucurónidos/análisis , Hígado/química , Fenoles/análisis , Animales , Compuestos de Bencidrilo/metabolismo , Cromatografía Líquida de Alta Presión , Femenino , Glucurónidos/metabolismo , Hígado/metabolismo , Masculino , Perfusión , Fenoles/metabolismo , Ratas , Ratas Sprague-Dawley , Sulfatos/análisis , Sulfatos/metabolismoRESUMEN
Extensive studies are published concerning the distribution of monocarboxylate transporters (MCTs) in various animal issues including ruminants; nonetheless, nothing is known about their cellular expression and localization in the ruminant pancreas. The present study was carried out to examine the expression and cellular localization of all the fourteen MCT isoforms in cattle pancreas. RT-PCR verified the existence of mRNA transcripts for eight MCT isoforms, namely, MCT1, MCT2, MCT3, MCT4, MCT5, MCT8, MCT13, and MCT14 in cattle pancreas. Western blotting analysis confirmed the protein expression of these eight MCTs in the cattle pancreatic tissue. Immunohistochemical study, within the whole pancreas, was conducted to localize the eight MCTs identified, and the results showed strong positive immunoreactive staining for MCT1, MCT2, MCT4, MCT5, MCT13, and MCT14 on nearly all the islet cells of Langerhans, while we could not detect immunopositive signals in the acinar cells with any of MCTs antibodies used. This study, for the first time, showed the cellular localization and expression of MCT1-MCT5, MCT8, MCT13, and MCT14 within the ruminant pancreas. The distribution and expression pattern of MCT1, MCT2, MCT4, and CD147 in the cattle pancreas are different from that previously published on monogastric pancreas. Our study suggested that MCT1, MCT2, MCT4, MCT5, MCT13, and MCT14 may participate in the regulation of the pancreatic endocrine secretions in ruminants.
Asunto(s)
Regulación de la Expresión Génica , Islotes Pancreáticos/metabolismo , Transportadores de Ácidos Monocarboxílicos/genética , Transportadores de Ácidos Monocarboxílicos/metabolismo , Animales , Western Blotting , Bovinos , Femenino , Glucagón/metabolismo , Inmunohistoquímica , Insulina/metabolismo , Reacción en Cadena de la Polimerasa , Isoformas de Proteínas , Transporte de ProteínasRESUMEN
Fourteen members of the monocarboxylate transporter (MCT, SLC16) family have been identified, each having a different tissue distribution and substrate specificity. The expression of monocarboxylate transporters MCT1 and MCT4 have been studied in the gastrointestinal tract of ruminants; however, details of the expression of other MCT isoforms in the various parts of ruminant gastrointestinal tract are lacking. Reverse transcription with the polymerase chain reaction was used to study the regional distribution of MCT2, MCT3, and MCT5-MCT14 in the cattle gastrointestinal tract and verified the existence of MCT mRNA transcripts for MCT2, MCT3, MCT4, MCT7, MCT8, MCT9, MCT10, MCT13, and MCT14 in the ruminal and abomasal epithelia, mRNA transcripts for MCT2, MCT3, MCT4, MCT7, MCT8, MCT10, MCT13, and MCT14 in the jejunum, and mRNA transcripts for MCT2, MCT3, MCT4, MCT7, MCT8, MCT13, and MCT14 in the caecum of cattle. At the cellular level, immunohistochemical studies localized MCT2, MCT7, and MCT8 proteins in the cattle rumen, abomasum, jejunum, and caecum. This is the first study to detect the expression of various MCT isoforms in the gastrointestinal tract of a ruminant species. Our data suggest that these transporter proteins are involved in essential physiologic processes and are possible molecular targets for studying the regulation of the transport of short-chain monocarboxylates, aromatic amino acids, and thyroid hormones across the gastrointestinal tract of cattle.
Asunto(s)
Tracto Gastrointestinal/citología , Tracto Gastrointestinal/metabolismo , Transportadores de Ácidos Monocarboxílicos/metabolismo , Abomaso/citología , Abomaso/metabolismo , Secuencia de Aminoácidos , Animales , Bovinos , Ciego/citología , Ciego/metabolismo , Datos de Secuencia Molecular , Transportadores de Ácidos Monocarboxílicos/química , Transportadores de Ácidos Monocarboxílicos/genética , Transporte de Proteínas , ARN Mensajero/genética , ARN Mensajero/metabolismo , Rumen/citología , Rumen/metabolismoRESUMEN
Fatty acid-binding protein (FABP) has high affinity for long-chain fatty acids and appears to participate in the metabolism and intracellular transport of lipids. Liver- and intestinal-type FABP (L-FABP and I-FABP, respectively) are expressed in the small intestine. However, in the gastrointestinal tract of ruminants, expression and localization of FABPs are unknown. In this study, we investigated the expression of I-FABP and L-FABP in the gastrointestinal tract of cattle. I- and L-FABP had higher messenger RNA (mRNA) and protein expression levels in the duodenum and jejunum relatively to other gastrointestinal regions in both calves and cows. Furthermore, L-FABP mRNA and protein expression were high in the colon. Both these protein types were confirmed to be in the cytosol of jejunal epithelial cells, where they were found in the villi rather than in the crypts. We concluded that duodenal and jejunal FABPs might be involved in the metabolism of fatty acids mainly in epithelial cells in cattle.
Asunto(s)
Bovinos/metabolismo , Células Epiteliales/metabolismo , Proteínas de Unión a Ácidos Grasos/metabolismo , Ácidos Grasos/metabolismo , Tracto Gastrointestinal/metabolismo , Metabolismo de los Lípidos , Animales , Colon/metabolismo , Citosol/metabolismo , Duodeno/metabolismo , Proteínas de Unión a Ácidos Grasos/genética , Femenino , Expresión Génica , Yeyuno/metabolismo , Masculino , ARN Mensajero/metabolismo , Rumen/metabolismoRESUMEN
This study is the first to examine the expression of the 14 monocarboxylate transporter genes (MCT1-MCT14) in the mammary gland of mammals. RT-PCR, Western blot, immunohistochemistry, and immunofluorescence confocal laser microscopy were applied in a comprehensive approach to assess the expression and cellular localization of MCTs in the mammary gland of lactating cattle. RT-PCR revealed the existence of nine MCT isoforms, namely MCT1, MCT2, MCT3, MCT4, MCT5, MCT8, MCT10, MCT13, and MCT14 in cow mammary gland. The amplified cDNA segments were confirmed by sequence analysis and deposited in the GenBank. Using the commercially available antibodies against MCT1-MCT8, Western blotting verified the protein expression of MCT1, MCT2, MCT3, MCT4, MCT5, and MCT8 in the cow mammary gland. The precise cellular localization of the identified MCT proteins showed that both MCT1 and MCT2 were basolaterally localized on the cow mammary alveolar epithelial cells. In contrast, MCT4 protein signal was expressed on the apical membrane of these alveolar epithelia. MCT8, however, was predominantly localized on the basolateral membranes of the lactocytes, along with its weak labeling on the apical membrane of the same cells. No immunoreactive staining for MCT3 and MCT5 proteins could be detected histochemically in lactating bovine mammary tissue. Additionally, we proved the colocalization of CD147 with both MCT1 and MCT4 on the boundaries of the cow mammary alveolar epithelia. The existence and localization pattern of MCT genes in the mammary gland of lactating cows suggest their possible involvement in the transport of essential elements required for milk synthesis and secretion.
Asunto(s)
Basigina/metabolismo , Lactancia/metabolismo , Glándulas Mamarias Animales/metabolismo , Transportadores de Ácidos Monocarboxílicos/metabolismo , Animales , Bovinos , Femenino , Lactancia/genética , Glándulas Mamarias Animales/citología , Transportadores de Ácidos Monocarboxílicos/genética , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , ARN Mensajero/metabolismoRESUMEN
This work was undertaken to study the effect of pectin feeding on the expression level, cellular localization and functional activity of monocarboxylate transporter 1 (MCT1) in the gastrointestinal tract of rats. The results indicated that MCT1 protein level was significantly increased along the entire length of the gastrointestinal tract of pectin-fed rats in comparison with control animals. Immunohistochemical analysis revealed an increase in MCT1 in the stratified squamous epithelia of the forestomach as well as in the basolateral membranes of the cells lining the gastric pit of the glandular stomach of pectin-fed rats when compared with control animals. The parietal cells, which showed barely any or no detectable MCT1 in the control group, exhibited a strong intensity of MCT1 on the basolateral membranes in pectin-fed rats. In the small intestine of pectin-fed rats, strong immunopositivity for MCT1 was detected in the brush border and basolateral membranes of the absorptive enterocytes lining the entire villi, while in control rats, weak reactivity was detected on the brush border membrane in a few absorptive enterocytes in the villus tip. In the large intestine of control animals, MCT1 was detected on the basolateral membranes of the epithelia lining the caecum and colon. This staining intensity was markedly increased in pectin-fed rats, along with the appearance of strong reactivity for MCT1 on the apical membranes of the surface and crypt epithelia of caecum and colon. Our results also showed that MCT1 co-localizes with its chaperone, basigin (CD147), in the rat gastrointestinal tract, and that the pectin feeding increased the expression of CD147. In vivo functional studies revealed an enhanced acetate absorption in the colon of pectin-fed in comparison with control animals. We conclude that MCT1 is up-regulated along the gastrointestinal tract of pectin-fed rats, which might represent an adaptive response to the increased availability of its substrates.
Asunto(s)
Fibras de la Dieta/administración & dosificación , Intestinos/efectos de los fármacos , Transportadores de Ácidos Monocarboxílicos/metabolismo , Pectinas/administración & dosificación , Estómago/efectos de los fármacos , Simportadores/metabolismo , Acetatos/metabolismo , Animales , Basigina/metabolismo , Proteínas Sanguíneas/metabolismo , Mucosa Gástrica/efectos de los fármacos , Mucosa Gástrica/metabolismo , Absorción Intestinal , Mucosa Intestinal/efectos de los fármacos , Mucosa Intestinal/metabolismo , Cinética , Masculino , Microvellosidades/efectos de los fármacos , Microvellosidades/metabolismo , Transportadores de Ácidos Monocarboxílicos/antagonistas & inhibidores , Ratas , Ratas Sprague-Dawley , Simportadores/antagonistas & inhibidores , Regulación hacia Arriba , Ácido p-Cloromercuribenzoico/farmacologíaRESUMEN
This study provides novel information regarding the existence and precise cellular localization of various monocarboxylate transporters (MCTs) in the mammalian adrenal gland. RT-PCR results revealed that 10 MCT isoforms, namely MCT1, MCT2, MCT3, MCT4, MCT5, MCT8, MCT9, MCT10, MCT13, and MCT14 are expressed in the bovine adrenal gland. MCTs (MCT1-MCT8) proteins were examined by Western blot analysis in the bovine adrenal gland. The precise cellular localization of six MCT isoforms (MCT1-MCT5 and MCT8) within the different zones of the adrenal gland has been determined by immunohistochemical and immunofluorescence confocal laser microscopy analyses. To gain insight on the species differences for the expression profiles of MCT isoforms in this vital organ, we also examined the expression and cellular localization of MCT1-MCT8 in the rat adrenal gland. Some discrepancies in MCTs profiles between cattle and rat have been observed in the different zones of the adrenal gland. The tissue distribution pattern of MCT isoforms in the steroid-secreting adrenal cortex and catecholamine-secreting adrenal medulla suggests that they may play distinct roles in the regulation of the different hormone biosynthesis in the adrenal gland. Also, it is possible that different MCT isoforms in adrenal gland can be differentially regulated under acute or chronic conditions. This report can form the basis for future research on the regulation of these transporters in the adrenal gland.
Asunto(s)
Glándulas Suprarrenales/metabolismo , Bovinos/metabolismo , Transportadores de Ácidos Monocarboxílicos/metabolismo , Animales , Bovinos/genética , Femenino , Expresión Génica , Masculino , Transportadores de Ácidos Monocarboxílicos/genética , Familia de Multigenes , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Distribución TisularRESUMEN
In this study, the expression and distribution of monocarboxyolate transporter 1 (MCT1) along the intestines (duodenum, jejunum, ileum, cecum, colon and rectum) of dogs were investigated at both the mRNA and protein levels. The expression of MCT1 protein and its distribution were confirmed by Western blotting and immunohistochemical staining using the antibody for MCT1. We identified mRNA coding for MCT1 and a 43-kDa band of MCT1 protein in all regions from the duodenum to the rectum. Immunoreactive staining for MCT1 was also observed in epithelial cells throughout the intestines. MCT1 immunoreactivity was greater in the large intestine than in the small intestine. MCT1 protein was predominantly expressed on the basolateral membranes along intestinal epithelial cells, suggesting that MCT1 may play an important role in lactate efflux and transport of short-chain fatty acids (SCFAs) to the bloodstream across the basolateral membranes of the dog intestine.
Asunto(s)
Perros/genética , Perros/metabolismo , Regulación de la Expresión Génica , Mucosa Intestinal/metabolismo , Transportadores de Ácidos Monocarboxílicos/genética , Transportadores de Ácidos Monocarboxílicos/metabolismo , Simportadores/genética , Simportadores/metabolismo , Animales , Intestinos/citología , ARN Mensajero/metabolismoRESUMEN
This is the first study to determine the precise cellular localization of monocarboxylate transporter 4 (MCT4), along with its co-existence with its chaperone, CD147 in the ruminant gastrointestinal tract. Quantitative Western blot analysis demonstrated that the abundance of MCT4 protein was in the order of forestomach > large intestine > abomasum >or= small intestine. Immunohistochemistry and immunofluorescence confocal laser microscopy showed that MCT4 in the forestomach was confined to the cell membranes of strata corneum and granulosum, while diffuse cytoplasmic staining for MCT4 was visualized in strata spinosum and basale. In the epithelium cells lining the abomasum, MCT4 immunoreactive positivities were predominantly localized on the basolateral membranes. In the small intestine, MCT4 was localized at the brush borders and the basolateral membranes of the epithelial cells lining the villi, however it was mostly found on the apical membranes of the crypt cells. In the large intestine, the immunoreactivity for MCT4 differed between the surface epithelium and the crypts; in the surface epithelium, MCT4 was mainly localized at the apical membranes, whereas in the crypts it was predominantly expressed on the basolateral membranes of the lining epithelial cells. MCT4 was remarkably co-existed with CD147 along the bovine gastrointestinal tract. Our results suggest that MCT4 can play an important role in the transport of SCFA. The study also explored the potential functional collaboration between MCT1 and MCT4 and provided new insights into the mechanisms that mediate the transport of SCFA and other monocarboxylates in the different segments of the ruminant gastrointestinal tract.
Asunto(s)
Tracto Gastrointestinal/química , Transportadores de Ácidos Monocarboxílicos/análisis , Rumiantes/metabolismo , Análisis de Varianza , Animales , Basigina/análisis , Western Blotting , Bovinos , Tracto Gastrointestinal/citología , Inmunohistoquímica , Intestino Grueso/química , Intestino Grueso/citología , Intestino Delgado/química , Intestino Delgado/citología , Microscopía Confocal , Transportadores de Ácidos Monocarboxílicos/biosíntesis , Transportadores de Ácidos Monocarboxílicos/fisiología , Músculo Liso/química , Músculo Liso/citología , Estómago/química , Estómago/citologíaRESUMEN
Despite the importance of short-chain fatty acids (SCFA) in maintaining the ruminant physiology, the mechanism of SCFA absorption is still not fully studied. The goal of this study was to elucidate the possible involvement of monocarboxylate transporter 1 (MCT1) in the mechanism of SCFA transport in the caprine rumen, and to delineate the precise cellular localization and the level of MCT1 protein along the entire caprine gastrointestinal tract. RT-PCR revealed the presence of mRNA encoding for MCT1 in all regions of the caprine gastrointestinal tract. Quantitative Western blot analysis showed that the level of MCT1 protein was in the order of rumen >/= reticulum > omasum > caecum > proximal colon > distal colon > abomasum > small intestine. Immunohistochemistry and immunofluorescence confocal analyses revealed widespread immunoreactive positivities for MCT1 in the caprine stomach and large intestine. Amongst the stratified squamous epithelial cells of the forestomach, MCT1 was predominantly expressed on the cell boundaries of the stratum basale and stratum spinosum. Double-immunofluorescence confocal laser-scanning microscopy confirmed the co-localization of MCT1 with its ancillary protein, CD147 in the caprine gastrointestinal tract. In vivo and in vitro functional studies, under the influence of the MCT1 inhibitors, p-chloromercuribenzoate (pCMB) and p-chloromercuribenzoic acid (pCMBA), demonstrated significant inhibitory effect on acetate and propionate transport in the rumen. This study provides evidence, for the first time in ruminants, that MCT1 has a direct role in the transepithelial transport and efflux of the SCFA across the stratum spinosum and stratum basale of the forestomach toward the blood side.
Asunto(s)
Ácidos Grasos Volátiles/metabolismo , Transportadores de Ácidos Monocarboxílicos/metabolismo , Rumen/metabolismo , Simportadores/metabolismo , Secuencia de Aminoácidos , Animales , Basigina/genética , Basigina/metabolismo , Femenino , Tracto Gastrointestinal/metabolismo , Regulación de la Expresión Génica , Cabras , Absorción Intestinal/fisiología , Mucosa Intestinal/metabolismo , Masculino , Datos de Secuencia Molecular , Transportadores de Ácidos Monocarboxílicos/análisis , Transportadores de Ácidos Monocarboxílicos/genética , ARN Mensajero/genética , ARN Mensajero/metabolismo , Simportadores/análisis , Simportadores/genéticaRESUMEN
The present study was undertaken to investigate the functional role of monocarboxylate transporter 1 (MCT1) in the ruminant large intestine. Messenger RNA encoding for MCT1 was verified by reverse transcriptase-polymerase chain reaction in caecum, proximal colon and distal colon of adult cattle. Both immunohistochemistry and confocal laser microscopy verified that the MCT1 protein was abundant in the surface epithelium of the large intestine, and the amount decreased from the opening of the crypt to its base. In the immunopositive cells, MCT1 was primarily localized in the basolateral membranes of epithelium lining the large intestine. Western blotting indicated that the levels of MCT1 protein were highest in the caecum, followed by proximal colon and then distal colon. In vitro studies were conducted to elucidate the possible involvement of MCT1 in the transport of short-chain fatty acids (SCFA) across the isolated mucosal sheets of cattle caecum using the Ussing chamber technique. Acetate absorption was found to be pH dependent, and the rate of acetate absorption increased as pH decreased. The serosal application of the MCT1 inhibitor 'p-chloromercuribenzoic acid (pCMB)' significantly reduced the transport of acetate across the caecal epithelium of cows. In addition, the transport of acetate was significantly reduced in the presence of its analogue, propionate, indicating that acetate and propionate compete for binding to the same transporter. The results show that MCT1 is a major route for SCFA efflux across the basolateral membrane of bovine large intestine and that it could play a role in the regulation of intracellular pH.
Asunto(s)
Ciego/metabolismo , Ácidos Grasos Volátiles/metabolismo , Transportadores de Ácidos Monocarboxílicos/metabolismo , Simportadores/metabolismo , Acetatos/metabolismo , Animales , Transporte Biológico/efectos de los fármacos , Transporte Biológico/fisiología , Bovinos , Colon/metabolismo , Femenino , Regulación de la Expresión Génica/fisiología , Concentración de Iones de Hidrógeno , Mucosa Intestinal/metabolismo , Transportadores de Ácidos Monocarboxílicos/genética , ARN Mensajero/genética , ARN Mensajero/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Reactivos de Sulfhidrilo/farmacología , Simportadores/genética , Factores de Tiempo , Ácido p-Cloromercuribenzoico/farmacologíaRESUMEN
In male rats challenged with the environmental estrogen bisphenol A, the compound is highly glucuronidated in the liver and is excreted largely into the bile. Given that in pregnancy the microsomal glucuronidation toward bisphenol A is attenuated, we hypothesized that elimination of bisphenol A from the liver may be reduced in pregnancy. This study was conducted to trace the elimination of bisphenol A in female rats, especially in pregnancy. In Sprague-Dawley rats, 1.5 mumol of bisphenol A was perfused into the liver via the portal vein. In both the male and the nonpregnant female, the infused bisphenol A was glucuronidated, then the resultant glucuronide was excreted mainly into the bile. In pregnant rats, however, bilious excretion of bisphenol A glucuronide was 60% of that observed in nonpregnant rats, and venous excretion increased reciprocally. During 1-h perfusion, total excretion of the glucuronide from the liver of male, nonpregnant female, and pregnant rats was 889.5 +/- 69.6, 1256.7 +/- 54.8, and 1038.8 +/- 33.3 nmoles, respectively. In Eisai hyperbilirubinemic rats (EHBR), perfusion of the liver with bisphenol A enabled us to determine that multidrug resistance-associated protein (MRP)2-mediating transport is the mechanism behind excretion of the glucuronide into the bile. The expression of MRP2 has been reported to be noticeably reduced in pregnancy. These results suggest that bisphenol A elimination by hepatic glucuronidation is slightly less in pregnancy than in non-pregnancy and that in pregnancy, more bisphenol A glucuronide is eliminated to the vein because of reduced MRP2 expression.
Asunto(s)
Glucurónidos/metabolismo , Hígado/metabolismo , Fenoles/metabolismo , Animales , Compuestos de Bencidrilo , Bilis/metabolismo , Femenino , Masculino , Proteínas de Transporte de Membrana/metabolismo , Proteína 2 Asociada a Resistencia a Múltiples Medicamentos , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/metabolismo , Embarazo , Ratas , Ratas Sprague-DawleyRESUMEN
UDP-glucuronosyltransferase is expressed in the proximal convoluted tubular cells of rat kidney. Kidney perfusion with a Krebs-Henseleit buffer containing 1-naphthol was performed to estimate the dynamics and disposition of the glucuronide conjugate formed in the epithelial cells of the renal tubules. When 1-naphthol was injected into the renal artery, and the perfusate from the renal vein was returned to a reservoir and recirculated through the kidney preparation (recirculating perfusion), most of the 1-napthol was immediately excreted into the vein as a glucuronide conjugate and its concentration increased rapidly. In contrast, the 1-napthol glucuronide appeared more slowly in the urine. 1-Naphthol was also injected during the initial 5 min of perfusion under single-pass perfusion conditions (single-pass perfusion) in situ, and the metabolite and parent compound in the venous perfusate and in urine were assayed. Under this condition, most of the 1-naphthol glucuronide was excreted into the renal vein, and not urine. Phenol UDP-glucuronosyltransferase was highly induced in the rat kidney by beta-naphthoflavone treatment. Moreover, the amount of 1-naphthol glucuronide excreted in the renal vein was increased 2.7-fold in the perfused kidney of beta-naphthoflavone-treated rats, but the amount in the urine was not significantly increased under singlepass perfusion conditions. These results indicate that the kidney can glucuronidate phenolic xenobiotics in epithelial cells of the tubules and excrete the resultant glucuronide into the renal vein.
Asunto(s)
Glucurónidos/metabolismo , Riñón/irrigación sanguínea , Riñón/metabolismo , Naftoles/metabolismo , Venas Renales/metabolismo , Animales , Cromatografía Líquida de Alta Presión , Inducción Enzimática , Glucurónidos/orina , Glucuronosiltransferasa/biosíntesis , Técnicas In Vitro , Riñón/enzimología , Túbulos Renales/metabolismo , Masculino , Microsomas/enzimología , Naftoles/orina , Perfusión , Ratas , Ratas Sprague-Dawley , Factores de Tiempo , Urotelio/metabolismo , beta-naftoflavona/farmacologíaRESUMEN
Nonylphenol, an environmental estrogenic chemical, is reported to have adverse effects on the reproductive organs of animals. In this study, the metabolism of nonylphenol and that of other alkylphenols in the rat liver was investigated using liver perfusion. Alkylphenols (nonylphenol, hexylphenol, butylphenol, and ethylphenol) were glucuronidated by rat liver microsomes. Nonylphenol was found to be conjugated with glucuronic acid by an isoform of UDP-glucuronosyltransferase, UGT2B1, expressed in yeast AH22 cells. However, when nonylphenol was perfused into rat liver in situ, it was difficult for free nonylphenol and conjugated metabolite to be excreted into the bile or vein, and most of the perfused nonylphenol remained free and as a glucuronide conjugate in the liver tissue, even after 1 h of perfusion. After 1 h of perfusion of the other alkylphenols, most of them were excreted into the bile as glucuronides. Ethylphenol, which has the shortest alkyl chain, was excreted rapidly into both the bile and vein; however, the excretion rates of alkylphenols having longer alkyl chains tended to be slow. MRP-2-deficient Eisai hyperbilirubinemic rats could not secrete alkylphenol-glucuronides into the bile, indicating that alkylphenol-glucuronides are transported by MRP-2 to the bile in normal Sprague-Dawley rats. The results indicate that the kinetics of excretion of alkylphenol-glucuronides into the bile or vein depends on the length of alkyl chain and suggest that nonylphenol-glucuronide formed in the liver cannot be transported by MRP-2.
Asunto(s)
Glucurónidos/metabolismo , Hígado/efectos de los fármacos , Perfusión/métodos , Fenoles/metabolismo , Animales , Bilis/química , Bilis/metabolismo , Línea Celular , Conducto Colédoco , Inducción Enzimática/efectos de los fármacos , Inducción Enzimática/genética , Expresión Génica/efectos de los fármacos , Expresión Génica/genética , Glucuronosiltransferasa/biosíntesis , Glucuronosiltransferasa/genética , Glucuronosiltransferasa/metabolismo , Hepatocitos/química , Hepatocitos/efectos de los fármacos , Hepatocitos/metabolismo , Hiperbilirrubinemia Hereditaria/genética , Hiperbilirrubinemia Hereditaria/metabolismo , Hígado/química , Hígado/metabolismo , Masculino , Microsomas Hepáticos/enzimología , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/fisiología , Fenoles/administración & dosificación , Fenoles/farmacocinética , Vena Porta , Ratas , Ratas Mutantes , Ratas Sprague-Dawley , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Relación Estructura-Actividad , Factores de Tiempo , Uridina Difosfato Ácido Glucurónico/metabolismoRESUMEN
Bisphenol A, an environmental estrogen, can be leached from plastic tableware and from the coating of food and drink cans, orally exposing human beings to the compound. The present study focuses on the absorption and metabolism of bisphenol A in the rat intestine, as elucidated experimentally by segmented everted intestine. One hour after the application of 2 micromol of bisphenol A to the mucosal fluid, the absorption of bisphenol A was slightly greater in the colon (48.6%) than in the proximal jejunum (37.5%). In the serosal side, unconjugated bisphenol A appeared in small amounts, increasing distally (maximal 1.6 nmol, colon). Large amounts of the bisphenol A glucuronide were then transported into the serosal side, also increasing distally (proximal, 80.4 nmol; distal, 478.4 nmol). The greatest amount of the glucuronide (approximately 573 nmol) was excreted into the mucosal side of the small intestine, whereas in the colon, mucosal excretion was minimal (67.2 nmol). On high-dose application of bisphenol A to the mucosal fluid, the transported unconjugated bisphenol A increased markedly throughout the intestine and colon. These results suggest that bisphenol A in the intestinal lumen is glucuronidated almost exclusively during its passage through the intestinal wall.
Asunto(s)
Glucurónidos/metabolismo , Absorción Intestinal/fisiología , Mucosa Intestinal/metabolismo , Fenoles/metabolismo , Animales , Compuestos de Bencidrilo , Masculino , Ratas , Ratas Sprague-DawleyRESUMEN
In the last two decades, multiple aspects of the peptide YY (PYY) secretion have been investigated. Besides fat and fatty acids, many luminal nutrients in the distal intestine appear to induce PYY release. Some studies have shown that bile acid, but not nutrients, plays a crucial role in the regulation of PYY secretion. Moreover, chyme in the proximal intestine also regulates the peptide release by indirect action through humoral and neuronal factors. Gastrin, cholecystokinin, and the vagus nerve are major candidates for mediators of these indirect actions. Several growth factors have been shown to regulate PYY synthesis in mucosa of the distal intestine. This review is aimed at presenting an overview of these recent studies on PYY secretion in the distal intestine.