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A C Delorme

Publications and source records attributed to A C Delorme.

10 recordsLinked to original sources
PubMed1985

Presence of immunoreactive vitamin D-binding protein in rat yolk sac endodermal cells.

The visceral yolk sac is, in the rat, an organ which possesses true placental functions. We recently showed that yolk sac is involved in the control of metabolism and action of vitamin D in the fetoplacental unit, since its endodermal cells contain a 24-hydroxylase for vitamin D metabolites and the 1,25-dihydroxyvitamin D receptor. In the present work, by using indirect immunoperoxidase staining, we demonstrate that an immunoreactive vitamin D-binding protein (DBP) is present in this yolk sac throughout embryonic and fetal development. It is mainly located at the apex of the endodermal cells. Immunoprecipitation studies of radioactive proteins synthesized in vitro by yolk sac explants showed that yolk sac DBP, in contrast to alpha-fetoprotein, is not synthesized in situ by yolk sac. This result, combined with the location of DBP at the apex of the endodermal cells which face the uterus, strongly suggests that yolk sac DBP is of maternal origin. The concomitant presence in the endodermal cells of this DBP, of the 1,25-dihydroxyvitamin D receptor, and of the system hydroxylating vitamin D metabolites in position 24, certainly has considerable physiological significance.

Animals↗
PubMed1983

Biochemical evidence for the presence of two vitamin D-dependent calcium-binding proteins in mouse kidney.

Mouse kidney, a vitamin D target organ, was investigated for the presence of vitamin D-dependent calcium-binding proteins (CaBP). Mouse kidney cytosol was fractionated by several biochemical methods including gel filtration chromatography, gel permeation high performance liquid chromatography, and chromatofocusing. Mouse kidney was found to possess two CaBPs which completely differed biochemically and exhibited no cross-immunoreactivity. One had a molecular weight of 25,000 and a pI of 5.9. The other, with a molecular weight of 10,000 and a pI of 4.9, was biochemically identical with mouse duodenal 10,000 CaBP. In addition, mouse renal and duodenal 10,000 CaBPs were immunologically identical. Moreover, the 10,000 CaBP was the predominant CaBP in mouse kidney since the latter contained about twice as much 10,000 CaBP as 25,000 CaBP (in mol/mg of renal cytosolic protein). In vitro incorporation of [3H]leucine into renal 10,000 CaBP demonstrated that it is synthesized in situ by mouse kidney. Renal 10,000 CaBP was already present during fetal life, and reached its adult level during the first week after birth. The vitamin D dependency of both mouse renal 10,000 and 25,000 CaBPs was assessed by their decrease in vitamin D-deficient mice and subsequent rise after 1,25-dihydroxyvitamin D3 injection. The concomitant presence of substantial amounts of two vitamin D-dependent CaBPs in mouse kidney is peculiar to this organ, which might consequently provide a unique model for studying the hormonal expressions of 1,25-dihydroxyvitamin D3.

Animals↗
PubMed1983

In rat uterus 17 beta-estradiol stimulates a calcium-binding protein similar to the duodenal vitamin D-dependent calcium-binding protein.

A calcium-binding protein (CaBP) similar to rat duodenal vitamin D-dependent CaBP was identified in rat uterus. Uterine CaBP and duodenal CaBP had the same mol wt (9,000-10,000), exhibited the same calcium-dependent electrophoretic mobility, and were immunologically identical. The localization of CaBP in the rat uterus was explored using indirect immunoperoxidase methods, and by CaBP RIA in the endometrium and myometrium after enzyme separation. In the endometrium CaBP was found in the cytoplasm of the stroma cells but not in the epithelium or in the glandular cells. In the myometrium, it was located inside the smooth myometrial fibers. Hormonal regulation of CaBP was shown to differ in the uterus and duodenum. Duodenal CaBP concentrations increased in response to 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), and were not influenced by ovariectomy or sex steroids administration. By contrast, CaBP synthesis fell drastically in the uterus of ovariectomized rats, but was greatly enhanced by low physiological doses of 17 beta-estradiol. This effect of 17 beta-estradiol on uterine CaBP was dose dependent. Medroxyprogesterone and more especially 1,25(OH)2D3 exerted no such stimulating effect on uterine CaBP. In vitamin D-deficient ovariectomized rats, administration of 17 beta-estradiol alone restored the uterine CaBP concentrations to normal and this potency contrasted with the apparent inability of 1,25(OH)2D3 to affect the uterine CaBP concentrations. Our data suggest that, unlike duodenal CaBP regulation, the expression of the CaBP gene in rat uterus is predominantly controlled by 17 beta-estradiol.

Animals↗
PubMed1982

Presence of 25-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3 24-hydroxylase in vitamin D target cells of rat yolk sac.

In the pregnant rat, the yolk sac, which possesses true placental functions, is a vitamin D target organ. We tested its ability to hydroxylate 25-hydroxy- and 1,25-dihydroxyvitamin D3 (25-OHD3 and 1,25-(OH)2D3). 24,25-Dihydroxy- and 1,24,25-trihydroxyvitamin D3 were produced by rat yolk sac homogenates incubated with tritiated 25-OHD3 and 1,25-(OH)2D3. Rat yolk sac homogenates also formed small amounts of 25,26-dihydroxyvitamin D3. These newly synthesized metabolites were isolated and identified by Sephadex LH-20 chromatography, high performance liquid chromatography, and periodate cleavage. Yolk sac 25-OHD3- and 1,25-(OH)2D3-24-hydroxylases were present in mitochondria and were of a mixed function oxidase nature. They were detected in the yolk sac as early as day 12 in the embryonic period and until the end of gestation. No hydroxylation occurred in maternal liver, amnion, fetal brain, or skin homogenates. Both 24-hydroxylases were detected in pure isolated rat yolk sac endodermal cells. This may be of physiological importance, since they are the 1,25-(OH)2D3 target cells in the yolk sac. Injection of 1,25-(OH)2[3H]D3 into rat yolk sac vitelline veins strongly suggested that the yolk sac vitelline veins strongly suggested that the yolk sac produced 1,24,25-(OH)3D3 in vivo. We conclude that the yolk sac and more precisely its endodermal cells may help to control vitamin D metabolism within the fetoplacental unit.

Animals↗
PubMed1982

Biochemical characterization of mouse vitamin D-dependent calcium-binding protein. Evidence for its presence in embryonic life.

We compared immunochemical and biochemical properties of the vitamin D-dependent Ca2+-binding protein (CaBP) from rat and mouse intestine. The two intestinal CaBP species were extensively purified by gel filtration and successive anion-exchange chromatographies. Both had a similar mol.wt. of 9000. Their pI values differed markedly, being 8.0 and 4.9 in rat and mouse CaBP respectively. Accordingly, mouse CaBP displayed more anodal migration in electrophoresis under non-denaturing conditions. Both mouse and rat CaBP only exhibited partial immunochemical similarities, but their amino acid compositions were very similar. Chromatofocusing was also found to be a good method of detecting calcium-dependent changes in their pI. We developed a sensitive radioimmunoassay for mouse CaBP enabling us to detect substantial amounts of CaBP in uterus, yolk sac and chorio-allantoic placenta. During normal mouse gestation, CaBP appeared on day 12 in the chorio-allantoic placenta but was already present on day 9 in the yolk sac, where its level rose sharply between days 9.5 and 10. CaBP may therefore be considered as a new marker for mouse yolk-sac differentiation.

Amino Acids↗
PubMed1981

Biochemical evidence for a cytoplasmic 1 alpha,25-dihydroxyvitamin d3 receptor-like protein in rat yolk sac.

The yolk sac in rats is an organ of exchanges between the mother and fetus. A vitamin D-dependent calcium-binding protein (CaBP) has been recently described in this organ. This led us to investigate the presence of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) receptor-like proteins in the yolk sac cytosol. For this purpose we have utilized sucrose gradient centrifugation, Scatchard analysis, and DNA-cellulose chromatography. Our results show that cytosol prepared from rat yolk sacs contains a 3.3 S binding protein for 1,25-(OH)2D3. The binding is a highly specific, saturable process with high affinity(2 X 10(-10) M at 25 degrees C). The sterol-protein complex binds to DNA-cellulose. The 1,25-(OH)2D3 binding protein is present in the yolk sac from at least the 15th day until the 21st day of gestation. In contrast, such a binding protein is not found in the amnion, the other component of fetal membranes. The biochemical parameters of the 1,25-(OH)2D3 binding protein in the yolk sac are similar to those of 1,25-(OH)2D3 cytosolic receptors in vitamin D target organs. This strongly suggests that the 3.3 S protein in the yolk sac may function as a specific receptor, indicating that this organ may be a new target organ for vitamin D.

Animals↗
PubMed1981

Vitamin D3 metabolite injections to thyroparathyroidectomized pregnant rats: effects on calcium-binding proteins of maternal duodenum and of fetoplacental unit.

Fetomaternal relationships with respect to vitamin D metabolism were investigated in thyroparathyroidectomized (TPTX) pregnant rats, with or without treatment with different vitamin D3 metabolites. Calcium-binding protein (CaBP) in maternal duodenum was used as an index of 1,25-(OH)2D3 status of the mother. Pregnant rats were TPTX on day 12.5 and CaBP was measured on 21.5 days of gestation by RIA in maternal duodenal mucosa and in the fetoplacental unit (placenta, fetal membranes, and fetal intestine). In the duodenum of TPTX mothers, the CaBP concentration was reduced by 50%. This fall was associated with a decrease of 1,25-(OH)2D in maternal plasma. CaBP in maternal duodenum increased by the administration of 1,25-(OH)2D3 or 1,24,25-(OH)3D3. In contrast, 24,25-(OH)2D3 injections to TPTX mothers were ineffective. In both placenta and fetal membranes, CaBPs decreased by 20% in TPTX mothers and were normalized only in 1.25-(OH)2D3-treated TPTX mothers. In the fetal intestine, CaBP variations paralleled those of maternal duodenal CaBP. The data indicate that plasma levels of 1,25-(OH)2D in TPTX pregnant rats are partly under the control of maternal parathyroid glands, and they support that even in pregnancy, the CaBP concentration in maternal duodenum may well reflect the 1,25-(OH)2D status of the mother. The CaBP synthesis in placenta and fetal membranes are vitamin D-dependent, and their regulation differs from that of intestinal CaBP. It app]ears that 1 alpha-hydroxylase activities of the fetoplacental unit (placenta and fetal kidney) are blunted in TPTX animals and that CaBP synthesis in the fetus depends on the presence of 1 alpha-hydroxylated vitamin D3 metabolites in the mother.

24,25-Dihydroxyvitamin D 3↗
PubMed1979

Vitamin D-dependent calcium-binding protein. Changes during gestation, prenatal and postnatal development in rats.

During the perinatal period, calcium metabolism is stressed. As intestinal Ca-binding protein is considered as a molecular expression of the hormonal effect of 1,25-dihydroxycholecalciferol (1,25(OH)2D3), Ca-binding protin measurements may document the vitamin D roles during this period. We describe the variations of Ca-binding protein concentrations in the rat during the last 5 days of gestation, in the maternal duodenum, placentas, fetal membranes and fetal intestines. We also report intestinal Ca-binding protein changes from birth until weaning. The evolution of the maternal intestinal Ca-binding protein, which increases on day 19.5 of gestation, is consistent with that of calcium intestinal absorption and may be explained by increased 1,25(OH)2D3 production. Placental Ca-binding protein rises from day 17.5 until the end of gestation, and may be related to the profile of calcium transfer from mother to fetuses. It is noteworthy that the placental Ca-binding protein is predominantly found in the fetal part of the organ where materno-fetal exchanges occur. The yolk sac synthesizes substantial amounts of Ca-binding protein. In the fetal membranes, Ca-binding protein plateaus from day 17.5 until day 20.5 and decreases on day 21.5. The Ca-binding protein presence in the fetal placenta and in the yolk sac may suggest that these tissues are also targets for vitamin D. In the fetus the intestinal Ca-binding protein s is detected as early as day 17.5 of gestation and increases markedly during the last day of gestation. From birth and during the first 3 weeks of postnatal life, the intestinal Ca-binding protein concentration does not change. It undergoes a sharp rise just at the time of weaning. We have also shown that the specific distribution of Ca-binding protein along the intestine is acquired during intrauterine life and does not change with sucking or weaning. The two main changes of intestinal Ca-binding protein, observed just before birth and at weaning, may reflect the intestinal maturation and/or variations in vitamin D metabolism.

Aging↗
PubMedDate not supplied

Hormonal control of intestinal calcium-binding protein concentrations at weaning in rats.

In rats, the intestinal concentration of immunoreactive Ca-binding protein was shown to increase at weaning. We now report that injections of 1,25-dihydroxycholecalciferol (1,25(OH)2D3, 25 ng or 10 ng/day) in suckling rats on days 11, 12 and 13 induce a premature rise of the intestinal Ca-binding protein concentrations, associated with increased plasma Ca concentrations. No effect is seen after 25-hydroxycholecalciferol, or after hydrocortisone administration. L-Thyroxine, at high doses (50 micrograms/day) and at more physiological doses (2 micrograms/day) induces a significant rise of the intestinal Ca-binding protein concentrations and a decrease of plasma Ca concentrations. The association of 1,25(OH)2D3 (at 10 ng/day) and L-thyroxine (at 2 micrograms/day) does not cause an additive effect on Ca-binding protein concentrations and does not change plasma Ca. These results suggest that 1,25(OH)2D3 and thyroxine are probably involved in the regulatory mechanisms of the intestinal Ca-binding protein synthesis at weaning.

Animals↗