RESUMEN
Vitamin A is an important factor during gestation and its metabolite, retinoic acid (RA), is a potent teratogen. However, RA action on the placenta is still poorly understood. In this study we analysed the presence of RARs and RXRs in human trophoblastic cells. We determined that RAR alpha was the more expressed form in term placenta, and that RAR beta was induced by RA treatment. Then we analysed RA effects on endocrine activities and on epidermal growth factor (EGF) receptor expression. We found that RA decreased 125I-labeled EGF binding and EGF-dependent phosphorylation. Furthermore, RA treatment led to a concentration-dependent decrease in the amount of EGFR protein expression. This treatment also decreased EGF receptor mRNA levels, suggesting transcriptional regulation of the EGF receptor. Thus we demonstrated that RA could interact with feto-placental development by modulating trophoblast EGF receptors expression, probably via its nuclear receptors.
Asunto(s)
Receptores ErbB/análisis , Receptores de Ácido Retinoico/análisis , Tretinoina/toxicidad , Trofoblastos/química , Northern Blotting , Diferenciación Celular/efectos de los fármacos , Núcleo Celular/química , Núcleo Celular/ultraestructura , Células Cultivadas , Relación Dosis-Respuesta a Droga , Factor de Crecimiento Epidérmico/metabolismo , Receptores ErbB/efectos de los fármacos , Receptores ErbB/genética , Receptores ErbB/metabolismo , Femenino , Regulación del Desarrollo de la Expresión Génica/efectos de los fármacos , Humanos , Radioisótopos de Yodo , Proteínas Nucleares/análisis , Proteínas Nucleares/efectos de los fármacos , Proteínas Nucleares/genética , Placenta/química , Placenta/citología , Placenta/ultraestructura , Embarazo , Proteínas Tirosina Quinasas/metabolismo , ARN Mensajero/análisis , ARN Mensajero/genética , Receptores de Ácido Retinoico/efectos de los fármacos , Receptores de Ácido Retinoico/genética , Receptores de Ácido Retinoico/metabolismo , Receptores X Retinoide , Factores de Transcripción/análisis , Factores de Transcripción/efectos de los fármacos , Factores de Transcripción/genética , Transcripción Genética , Trofoblastos/citología , Trofoblastos/efectos de los fármacos , Trofoblastos/ultraestructuraRESUMEN
Human decidual cells are known to produce 1,25-(OH)2D3 at the end of pregnancy, the present study evaluates this capacity, and the part played by stromal decidual cells, in early pregnancy. Cells were obtained from nine human decidua by aspiration or curettage during early pregnancy (7-10 weeks), separated on Ficoll-Paque and plastic adherence, and incubated for 1 h with 25-(OH)D3. Incubation medium and cells were extracted and chromatographed on two successive HPLC systems. The cells examined were of both physiological and pathological (ectopic pregnancy) origin. Endometrial cells obtained in four non-pregnant situations (myomas) were also studied to determine whether the 1,25-(OH)2D3 synthesis by the uterus is associated with the appearance of decidual cells. Results show that human decidual cells from early pregnancy convert 25(OH)D3 (2.5 nM or 2.5 microM) into a metabolite with the physicochemical characteristics of synthetic 1,25-(OH)2D3. This ability is shared by cells isolated during early pregnancy, whether physiological or ectopic (tubal pregnancy). Non-adherent cells, which include mainly stromal decidual cells, are less able to produce 1,25-(OH)2D3 than are the adherent cells, suggesting that macrophages, granulocytes or as yet unidentified cell types are required for the 1,25-(OH)2D3 production by decidual tissue during early human pregnancy. In addition, one out of four experiments with non-pregnant endometrial cells could produce 1,25-(OH)2D3 suggesting that, although not the rule in the non-pregnant state, in vitro production of 1,25-(OH)2D3 by uterine cells can be found in the absence of decidual cells.
Asunto(s)
Calcitriol/biosíntesis , Primer Trimestre del Embarazo/metabolismo , Útero/metabolismo , Adhesión Celular , Cromatografía Líquida de Alta Presión , Decidua/citología , Decidua/metabolismo , Femenino , Humanos , Técnicas In Vitro , Embarazo , Útero/citologíaRESUMEN
The morphological and functional differentiation of human trophoblast cells ends with the formation of terminally differentiated multinucleated syncytial trophoblasts. This in vivo differentiation is mimicked in vitro during the primary culture of extravillous cytotrophoblasts: isolated mononuclear cytotrophoblasts aggregate and fuse to form syncytia. This in vitro differentiation is associated with an increase in epidermal growth factor receptor (EGF-R) expression and a transitory increase in E-cadherin expression during cell aggregation. In the present study, we investigated the expression of pp60c-src during morphological differentiation of trophoblast cells. Cultures were terminated at various time intervals and pp60c-src was analysed by immunocytochemistry using a specific antibody. In addition, pp60c-src was investigated by western blot analysis and its tyrosine kinase activity was measured concomitantly. In mononuclear cytotrophoblasts, pp60c-src was localized at cell-matrix contacts and during the aggregation of cytotrophoblasts, pp60c-src was distributed on the cell surface at points of cell-cell contact being colocalized with EGF-R and E-cadherin. The kinase activity of the pp60c-src protein increased significantly at day 2 when cells were completely aggregated and started to fuse, and remained elevated while cells underwent further differentiation. Inhibition of pp60c-src by herbimycin A at 0.25 to 1 microgram/ml during the first day of culture was associated with a decreased expression of tyrosine kinase activity of EGF-R and an increase in E-cadherin expression. These data suggest that pp60c-src is involved in the modulation of trophoblast cell aggregation and fusion leading to syncytial formation.
Asunto(s)
Proteínas Proto-Oncogénicas pp60(c-src)/metabolismo , Trofoblastos/metabolismo , Benzoquinonas , Cadherinas/metabolismo , Agregación Celular , Diferenciación Celular , Fusión Celular , Células Cultivadas , Receptores ErbB/efectos de los fármacos , Femenino , Células Gigantes/citología , Células Gigantes/metabolismo , Histocitoquímica , Humanos , Uniones Intercelulares/metabolismo , Lactamas Macrocíclicas , Embarazo , Proteínas Tirosina Quinasas/antagonistas & inhibidores , Proteínas Proto-Oncogénicas pp60(c-src)/efectos de los fármacos , Quinonas/farmacología , Rifabutina/análogos & derivados , Trofoblastos/citología , Trofoblastos/efectos de los fármacosRESUMEN
The purpose of this work was to investigate the effects of calcitonin (CT) on trophoblastic cells with respect to cAMP levels and human chorionic gonadotrophin (hCG) secretion in cultured cells from first-trimester and term placentas and in a choriocarcinoma cell line (JEG-3). The expression of the CT gene was investigated to elucidate a putative autocrine control of CT during pregnancy. The addition of salmon CT (10(-10) M and above) resulted in concentration-dependent increases in cAMP secretion by normal trophoblastic cells from term and first-trimester placentas. Moreover, CT was found to increase cAMP secretion preferentially in completely differentiated cells, i.e. after 4-7 days in culture. Addition to the culture medium of JEG-3 cells slightly increased cAMP secretion only at a concentration of 10(-8) M. The basal level of hCG in the medium was found to be higher in the first-trimester than in the term trophoblast culture, but salmon CT induced an increase in hCG secretion by term placenta cells only. CT gene expression in our experimental model was investigated to elucidate a putative autocrine control of CT action during pregnancy. It was not found to be expressed in syncytiotrophoblast cells from either first-trimester or term placenta cells by the method used. Our data demonstrate the absence of autocrine control of CT effects in trophoblastic cells, and suggest that CT is likely to exert its effect preferentially on differentiated cells.
Asunto(s)
Calcitonina/farmacología , Gonadotropina Coriónica/metabolismo , AMP Cíclico/metabolismo , Trofoblastos/efectos de los fármacos , Northern Blotting , Calcitonina/genética , Diferenciación Celular , Células Cultivadas , Coriocarcinoma/metabolismo , Femenino , Expresión Génica , Humanos , Hibridación de Ácido Nucleico , Embarazo , ARN/análisis , Trofoblastos/metabolismo , Células Tumorales CultivadasRESUMEN
Calcitriol or 1,25-dihydroxyvitamin D3 is synthesized by successive hydroxylations of vitamin D in the liver and kidney and during pregnancy in the placenta and the decidua. The aim of the present study was to clarify the immunoregulatory role of calcitriol, if any, during pregnancy. Calcitriol concentrations of 10(-10) to 10(-8) M was shown to reduce the proliferation of allogeneically stimulated lymphocytes and cytotoxic cell generation in a dose-dependent manner. However, calcitriol did not inhibit IL-2-dependent proliferation of CTLL-2 cell line. Calcitriol reduced non-MHC restricted cytotoxicity. Calcitriol, therefore, might be involved in the successful engraftment and growth of the fetoplacental unit possibly synergized with other products of placental or decidual origin.
Asunto(s)
Calcitriol/fisiología , Linfocitos/inmunología , Embarazo/inmunología , 24,25-Dihidroxivitamina D 3/farmacología , 24,25-Dihidroxivitamina D 3/fisiología , Calcitriol/farmacología , Línea Celular , Pruebas Inmunológicas de Citotoxicidad , Femenino , Humanos , Técnicas In Vitro , Células Asesinas Naturales/inmunología , Prueba de Cultivo Mixto de Linfocitos , Placenta/metabolismoRESUMEN
To clarify the biochemical mechanism responsible for the inhibition by calcitriol (1,25-dihydroxyvitamin D3) of cytotoxicity in peripheral blood lymphocytes (PBL), the human NK sensitive K562 cell line and the human tumor necrosis factor-sensitive murine L929 cell line were used as targets and subsequently compared. The cytotoxicity of PBLs for K562 cells was not changed by preincubation for 4 h with 10 ng/ml phorbol myristate acetate (PMA), but was reduced after an overnight preincubation with 10(-9) or 10(-8) M calcitriol. Using L929 cells, preincubation of PBLs with 10 ng/ml PMA for 4 h increased their cytotoxicity. Overnight incubation with calcitriol significantly reduced PBL cytotoxicity for L929 cells in a dose related manner and suppressed the enhancement of this cytotoxicity by PMA. Pretreatment of PBLs with cycloheximide reduced their cytolysis for L929 cells but did not change their cytotoxicity towards K562 cells. Consequently, the natural cytotoxicity of PBLs for K562 cells does not involve the same mechanism as their cytotoxicity for L929 cells and is therefore subject to different forms of regulation. However, calcitriol reduced PBL cytotoxicity towards both target cells.
Asunto(s)
Calcitriol/farmacología , Citotoxicidad Inmunológica/efectos de los fármacos , Linfocitos/inmunología , Línea Celular , Cicloheximida/farmacología , Humanos , Células Asesinas Naturales/inmunología , Acetato de Tetradecanoilforbol/farmacología , Factor de Necrosis Tumoral alfa/farmacologíaRESUMEN
The putative role of protein phosphorylation in modulating adenylate cyclase activity in polymorphonuclear neutrophil membranes was assessed using phorbol myristate acetate (PMA) to stimulate the activity of protein kinase C. PMA was demonstrated to enhance the adenylate cyclase activity stimulated by isoproterenol.
Asunto(s)
Adenilil Ciclasas/sangre , Neutrófilos/enzimología , Acetato de Tetradecanoilforbol/farmacología , Adenosina Trifosfato/metabolismo , Adulto , Membrana Celular/enzimología , AMP Cíclico/biosíntesis , Citosol/enzimología , Activación Enzimática , Humanos , Isoproterenol/farmacología , Neutrófilos/ultraestructura , Proteína Quinasa C/metabolismo , RadioinmunoensayoRESUMEN
The production of superoxide anion (O2-.) was measured in relation to 45Ca movement in glass-adherent polymorphonuclear leukocytes (PMNs), and the results were compared with those obtained by ourselves and others on PMNs in suspension. In adherent PMNs, O2-. production stimulated by N-formyl-methionyl-leucyl-phenylalanine (FMLP) was of rapid onset and short duration; this was also true of PMNs in suspension. However, O2-. production was insensitive to the concentration of extracellular calcium. Both in adherent and non-adherent PMNs, O2-. production stimulated with phorbol myristate acetate (PMA) had a latency time and was of long duration. In adherent PMNs, pretreatment with PMA potentiated the FMLP-induced O2-. production by lengthening its duration without changing its initial rate. In adherent PMNs (10(-10)-10(-7) M) FMLP induced a fast but transient dose-dependent increase in 45Ca within 1 min, whereas PMA only released 45Ca about 5 min after its addition to the cell culture medium. Pretreatment of PMNs with 10 or 100 ng/ml PMA for 3 min before stimulation by 10(-7) M FMLP reduced the 45Ca efflux observed with FMLP alone. We conclude that O2-. production by adherent PMNs cannot simply be related to Ca2+ movement. In comparison with non-adherent cells, adherence seemed to interfere with the characteristics of both calcium and O2-. generation, probably by modifying the cytoskeleton.
Asunto(s)
Calcio/metabolismo , Neutrófilos/metabolismo , Superóxidos/metabolismo , Adhesión Celular , Humanos , N-Formilmetionina Leucil-Fenilalanina/farmacología , Neutrófilos/efectos de los fármacos , Acetato de Tetradecanoilforbol/farmacologíaRESUMEN
The effect on vitamin D metabolite concentrations of insulin deficiency, not accompanied by hyperglycemia, were investigated in pregnant rats and in their fetuses injected with 75 mg/kg BW streptozotocin (SZ). These concentrations were measured in maternal plasma and whole fetal body. In the insulinopenic mothers, the 25OHD concentration was found to rise compared with that of control pregnant rats (7.00 +/- 1.66 ng/ml, n = 16, versus control 4.50 +/- 1.60, n = 10, 0.001 less than P less than 0.01). The concentration of 1,25(OH)2D, which was previously found to decrease in pregnant rats that were both hypoinsulinic and hyperglycemic, was previously found to decrease in pregnant rats that were both hypoinsulinic and hyperglycemic, was not different in our control and insulinopenic rats (107.36 +/- 38.25 pg/ml, n = 11, versus control 122.90 +/- 18.20, n = 18.20, n = 8). In fetuses from our SZ-injected rats, the 24,25(OH)2D level diminished compared with the control level (2.12 +/- 0.70 ng/g, n = 11, versus control 5.23 +/- 0.95 ng/g, n = 13, P less than 0.001). The Ca/P ratio in fetal body also decreased (0.68 versus control 1.12). It is suggested that the placental metabolism is an important determinant or normal fetal growth.
Asunto(s)
Glucemia/análisis , Feto/metabolismo , Insulina/deficiencia , Preñez/metabolismo , Vitamina D/metabolismo , Animales , Diabetes Mellitus Experimental/inducido químicamente , Diabetes Mellitus Experimental/metabolismo , Femenino , Feto/efectos de los fármacos , Intercambio Materno-Fetal , Embarazo , Ratas , Ratas Endogámicas , Estreptozocina/farmacologíaRESUMEN
The present study evaluates in osteosarcoma cells, the effects of a calcium channel inhibitor nicardipine in 24-hydroxylase activity and 45Ca desaturation curve in presence of 1,25-dihydroxycholecalciferol (1,25(OH)2D3). This sterol induced an increase in 24-OHase activity and 45Ca fluxes. Nicardipine reversed the effect of 1,25(OH)2D3 on 45Ca fluxes but reinforced the enhancement of the 24-OHase activity. The fact that the effects of 1,25(OH)2D3 were reduced by cycloheximide support the hypothesis of a de novo protein synthesis. Our study has allowed us to dissociate the effects of 1,25(OH)2D3 on 24-OHase enhancement from those on Ca2+ transport.
Asunto(s)
Calcitriol/farmacología , Calcio/metabolismo , Sistema Enzimático del Citocromo P-450 , Esteroide Hidroxilasas/metabolismo , Cicloheximida/farmacología , Humanos , Nicardipino/farmacología , Osteosarcoma , Biosíntesis de Proteínas , Proteínas/antagonistas & inhibidores , Células Tumorales Cultivadas , Vitamina D3 24-HidroxilasaRESUMEN
The effects of diltiazem, a calcium channel inhibitor, on the cellular transport of calcium were studied in isolated heterogenous rat bone cells. Efflux was measured after equilibrating the cells with 45Ca and adding the vitamin D metabolite (1,25dihydroxycholecalciferol-1,25(OH)2D3 or 24,25dihydrocholecalciferol-24,25(OH)2D3), the ionophore A23187 and/or diltiazem. Results were analysed by fitting the desaturation curve to a model of two exponential terms. Kinetic analyses of curve indicated the presence of 2 exchangeable pools with different rate constants of exchange between the medium and cells (expressed by K.). After incubation of bone cells with diltiazem (20 nmol/10(6) cells) the following changes were recorded: a marked decrease in the rate constant of efflux from the fast turnover calcium pool (K12) and a reduction of the calcium pool sizes. Incubation of 10(6) cells with 0.5 ng 1,25(OH)2D3 plus diltiazem significantly reduced K12 compared to incubation with 1,25(OH)2D3 alone. In presence of 24,25(OH)2D3, diltiazem did not significantly alter K12 which was raised by incubation with the metabolite alone. Ionophore A23187 (0.5 micrograms/10(6) cells) increased the value of slow turnover constants of efflux whose values were affected by diltiazem. The possible involvement of Ca movements in bone resorption does not seem confirmed in the present experiment since in vitro effects of diltiazem in organ culture (observed in an initial previous experiment) were not reflected in the calcium 45 desaturation kinetics in heterogenous bone cells.
Asunto(s)
Huesos/citología , Calcimicina/farmacología , Calcitriol/farmacología , Calcio/metabolismo , Dihidroxicolecalciferoles/farmacología , 24,25-Dihidroxivitamina D 3 , Animales , Huesos/diagnóstico por imagen , Huesos/metabolismo , Bloqueadores de los Canales de Calcio/farmacología , Radioisótopos de Calcio , Diltiazem/farmacología , Interacciones Farmacológicas , Cintigrafía , RatasRESUMEN
The effects of streptozotocin-induced diabetes on the vitamin D metabolism of pregnant rats were investigated in mothers and their fetuses, 11 and 14 days after streptozotocin (SZ) injection, i.e., on days 18 and 21 of gestation. In the mothers' plasma, the levels of 25-hydroxycholecalciferol (25OHD) and 1,25-dihydroxycholecalciferol (1,25(OH)2 D) were not different from control levels on day 18, but on day 21, 25OHD had increased, 1,25 (OH)2 D had diminished, and significant hypercalcemia was noted (10.1 +/- 0.27 mg/dl vs. 9.47 +/- 0.19 mg/dl, mean +/- SD). In hyperglycemic fetuses from the diabetic mothers, plasma insulin levels were reduced at day 18 but enhanced at day 21. 25OHD levels were not different from those of the controls at day 18, but were lower at day 21 (2.12 +/- 0.70 ng/g BW, n = 13, vs. 3.75 +/- 1.40 ng/g BW n = 29 controls, means +/- SD). Fetal body levels of 1,25 (OH)2 D were lower than that in the controls at day 18 (16.6 +/- 2.9 pg/g BW, n = 9 x 2, vs. 28.7 +/- 6.3 pg/g BW, n = 7 x 2, mean +/- SD P less than 0.001), but identical to control levels on day 21. The role of fetal or placental enzymes in the regulation of vitamin D metabolism in fetuses is discussed.
Asunto(s)
Diabetes Mellitus Experimental/fisiopatología , Feto/metabolismo , Preñez/metabolismo , Vitamina D/metabolismo , Animales , Diabetes Mellitus Experimental/inducido químicamente , Femenino , Feto/enzimología , Glucosa/análisis , Glucosa/metabolismo , Trastornos del Crecimiento/fisiopatología , Insulina/sangre , Insulina/metabolismo , Oxigenasas de Función Mixta/fisiología , Embarazo , Ratas , Ratas Endogámicas , Estreptozocina/farmacología , Vitamina D/análisisRESUMEN
Present knowledge of the alloantigenic status of the placenta, which makes it a natural semi-allogeneic allograft is briefly surveyed. The systemic immunoregulatory mechanisms operating during normal allopregnancy which are not a prerequisite for a successful pregnancy are recalled. The placenta--dependent local mechanisms, e.g. trophoblast dependent decidual suppressor cells, factor mediated and factor independent resistance to cell mediated lysis, are surveyed as well as some of the mechanisms of action of trophoblast regulatory factors, namely suppressor cell induction and inhibition of IL-2 dependent cell growth/activation. The main feature of the CBA x DBA/2 model of spontaneous abortions in mice, and its prevention by anti Balb/c leukocyte immunisation are described. It was shown that anti-T cell depletion prevents the anti-abortive effects of immunisation. Such a treatment is also able to restore normal placental weight in auto-immune MRL lpr mice, which are known to display excess seric CSF beta-like activity (CSFs being in vitro efficient growth factors for trophoblasts). Transfer of such cells into the MHC compatible CBA/J prevents resorbtions upon a subsequent mating with DBA/2. Thus, direct effects of CSFs beta 1 and beta 2 as anti abortifacient (IL3 and GM CSF) are described together with the abortificacient effects of TNFs and NKs activators.
Asunto(s)
Feto/inmunología , Isoantígenos/inmunología , Placenta/inmunología , Aborto Espontáneo/inmunología , Animales , Femenino , Humanos , Tolerancia Inmunológica , Embarazo , Linfocitos T/inmunologíaRESUMEN
Mouse skin fibroblasts in culture were used to study the regulation of 1,25-dihydroxycholecalciferol (1,25(OH)2D3) induced 24 hydroxylase (24-OH-ase) under the influence of 3 agents: (1) 24,25-Dihydroxycholecalciferol (24,25(OH)2D3), 62.5 10(-9) M, which led to a significant decrease in the 1,25(OH)2D3-induced 24-OH-ase, probably acted through a nuclear effect mediated by the 1,25(OH)2D3 receptor protein. (2) Triamcinolone acetonide (10(-6)M) which was found to increase the 24-OH-ase enhancement induced by 1.25 and 6.25 nM 1,25(OH)2D3 whereas it did not alter the effect of 31.2 nM 1,25(OH)2D3. (3) A factor which is likely to induce changes in the cell calcium transport or in the Ca pool sizes, i.e. a calcium channel blocker, nicardipine. The effect of 1.25 nM 1,25(OH)2D3 on 24-OH-ase activity was increased by nicardipine (20 microM) which was found to reduce the effect of 6.25 nM 1,25(OH)2D3. The rate of DNA synthesis (measured by [3H]thymidine incorporation) was increased after incubation of fibroblasts with 1,25(OH)2D3 (1.25 nM) plus triamcinolone acetonide (10(-6) M), although it was reduced by nicardipine in comparison with 1,25(OH)2D3 alone. So the effects of these agents on the 1,25(OH)2D3 induced 24-hydroxylase were shown to be independent of the rate of DNA synthesis.
Asunto(s)
Calcitriol/farmacología , Sistema Enzimático del Citocromo P-450 , Dihidroxicolecalciferoles/farmacología , Nicardipino/farmacología , Piel/enzimología , Esteroide Hidroxilasas/metabolismo , Triamcinolona Acetonida/farmacología , Animales , Células Cultivadas , Femenino , Fibroblastos/efectos de los fármacos , Fibroblastos/enzimología , Cinética , Masculino , Ratones , Ratones Endogámicos , Piel/efectos de los fármacos , Vitamina D3 24-HidroxilasaRESUMEN
Induction of diabetes in female rats by streptozotocin administration 7 days before mating led to an increase in maternal and fetal calcemia at day 21 of gestation. The plasma levels of 25-hydroxycholecalciferol (25 OH D3) were increased in the diabetic mother whereas the 25 OHD3 contents in entire fetuses were greatly decreased in comparison with control values obtained in both normal pregnant rat and normal fetuses. Our results obtained in pregnant rat were different from those found in the literature concerning non pregnant animals in which only 1,25-dihydroxycholecalciferol was affected by diabetes.
Asunto(s)
Calcifediol/sangre , Diabetes Mellitus Experimental/sangre , Sangre Fetal/análisis , Embarazo en Diabéticas/sangre , Animales , Glucemia/análisis , Calcio/sangre , Femenino , Fósforo/sangre , Embarazo , Ratas , Ratas Endogámicas , Vitamina D/metabolismoRESUMEN
The effect of the calcium antagonist diltiazem on bone resorption in organ culture has been investigated. It was found that diltiazem was ineffective alone but that in concentrations above 5 mumol/l it reduced mineral and organic resorption induced in vitro by 1.25 dihydroxycholecalciferol (1.25 (OH)2D3). No additivity with calcitonin effects was observed. Diltiazem did not significantly affect bone resorbing activity stimulated by 24,25(OH)2D3. Bone resorption was measured by an in vivo/in vitro technique using 45Ca prelabelled mice. Compared with 1.25(OH)2D3 alone treated group (0.480 pmol/g), it was found that diltiazem (100 nmol/g) reduced bone resorption without effect on calcium and phosphorus plasmatic concentrations at death. These data suggest that such a calcium antagonist is able to inhibit 1.25-(OH)2D3-increased-bone resorption either in vitro or in vivo/in vitro.
Asunto(s)
Benzazepinas/farmacología , Resorción Ósea/efectos de los fármacos , Diltiazem/farmacología , Animales , Calcitonina/farmacología , Calcitriol/farmacología , Calcio/metabolismo , Relación Dosis-Respuesta a Droga , Técnicas In Vitro , Mucosa Intestinal/metabolismo , RatonesRESUMEN
1,25-dihydroxyvitamin D3[1,25(OH)2D3] effects on bone resorption in organ culture and on 45Ca2+ efflux rates in bone cells were measured in presence of a calcium channel inhibitor, diltiazem. Though, diltiazem reduced the 45Ca release from mice calvaria it did not act at the same Ca compartment as 1,25(OH)2D3 to alter Ca2+ flux parameters. It therefore seems difficult to hypothesize a simple relationship between bone resorption and Ca2+ movements in bone cells.
Asunto(s)
Resorción Ósea/efectos de los fármacos , Huesos/metabolismo , Calcitriol/farmacología , Calcio/metabolismo , Animales , Huesos/efectos de los fármacos , Radioisótopos de Calcio , Diltiazem/farmacología , Ratones , Técnicas de Cultivo de Órganos , RatasRESUMEN
Two groups of female rats were used to investigate vitamin D metabolism in the pregnant animals and in their fetuses. In the first group, 3 micrograms of 25-hydroxyvitamin D3 (25-OH-D3) per kg of body weight were injected into intact or nephrectomized (NX) pregnant rats 3 h before sacrifice on day 21 of pregnancy; in the second group, 2 and 6 ng, respectively, of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) per day were infused continuously into pregnant rats between days 17 and 21 of pregnancy. The findings in the fetuses were obtained by quantitative analysis of extracts (Extrelut) of total fetal body lipids; the extracts were purified on Sep Pak and vitamin D sterols were further separated by high-pressure liquid chromatography. Three hours after the dams were injected with 25-OH-D3, the maternal plasma concentration (mean +/- SD) of 1,25(OH)2D3 was 221 +/- 84 pg/ml. In NX pregnant rats, the 1,25(OH)2D3 levels were still elevated: 95.6 +/- 49.0 pg/ml vs 45 +/- 22 pg/ml in control rats. In fetuses from intact or NX dams, the levels of 25-OH-D3 and 1,25(OH)2D3 were not different from the results obtained in the control fetuses but 24,25(OH)2D3 concentrations were increased (6.7 +/- 1.2 ng vs 2.2 +/- 0.7 ng/g body weight). After maternal infusion of 2 or 6 ng/day of 1,25(OH)2D3 (n = 8), plasma concentrations (mean +/- SD) of the metabolite were 64 +/- 31 and 517 +/- 356 pg/ml, respectively, the second being significantly higher than that of the control rats; 25-OH-D3 and 24,25(OH)2D3 levels did not change. 1,25(OH)2D3 contents (mean +/- SD) in fetuses from the treated dams were not different from those of control fetuses (10 +/- 2 pg/g body weight). Our results suggest that pregnant rats and their fetuses were protected against an excessive increase of 1,25(OH)2D3 concentrations in the maternal plasma; although there was some individual hypercalcemia, no significant increase in mean calcemia was detected in the dams, and 1,25(OH)2D3 either did not cross the placental barrier or was rapidly metabolized because we did not find any changes in the fetal content. As in intact or NX pregnant rats, 25-OH-D3 was metabolized into 1,25(OH)2D3, the increase of 24,25(OH)2D3 in the fetuses might be associated with a protective mechanism.
Asunto(s)
Calcifediol/farmacología , Calcitriol/farmacología , Feto/metabolismo , Vitamina D/metabolismo , Fosfatasa Ácida/metabolismo , Fosfatasa Alcalina/metabolismo , Animales , Calcifediol/metabolismo , Calcitriol/metabolismo , Calcio/sangre , Ergocalciferoles/análogos & derivados , Ergocalciferoles/metabolismo , Femenino , Masculino , Intercambio Materno-Fetal , Nefrectomía , Fosfatos/sangre , Embarazo , Ratas , Ratas EndogámicasRESUMEN
Fetal bone resorption was measured by an organ culture technique using fetuses from intact or thyroparathyroidectomized pregnant rats. These experiments were performed to investigate the effects of 1,25-dihydroxycholecalciferol (1,25-DHCC) and salmon calcitonin (SCT) in pregnant rats, on both fetal growth and fetal bone resorption. Pregnant rats were given 0.1-0.5 microgram 1,25-DHCC per day from day 17 of gestation: in intact rats bone resorption was increased and fetal growth decreased; 1,25-DHCC probably modified fetal bone resorption in the absence of fetal parathyroid secretion. Infusion of SCT in minipumps (30 mu./h) did not modify plasma calcium levels in either the mother or fetuses, neither was bone resorption altered. In 1,25-DHCC-treated rats, SCT infusion resulted in an increase in fetal weight and a decrease in fetal bone resorption. On the other hand, SCT infusion was found to facilitate phosphate accumulation in fetuses. At the end of the SCT infusion the SCT concentration was 450 ng/l in maternal plasma and 553 +/- 60 ng/l in fetal plasma. Salmon calcitonin was shown to cross the placental barrier in the rats; it may interact with the effects of 1,25-DHCC in the fetus.