Abstract
Pregnancy is associated with increased maternal calcium requirements that are met by enhanced intestinal calcium absorption. Maternal serum concentrations of total 1,25 are elevated, perhaps in response to a physiological hyperparathyroidism. An alternative explanation is that 1,25 produced by the fetoplacental unit gains access to the maternal compartment and influences maternal 1,25 status and intestinal calcium absorption. To test the hypothesis that fetal 1,25 gains access to the maternal intestine, we gave an intravenous injection of 20uCi of high specific activity (90 Ci/mmol) 3H-1,25 to a chronically catheterized fetal sheep at 138d of gestation (term=145d). Sequential samples of fetal and maternal plasma were obtained during the next 4 hours. Thereafter, samples of fetal and maternal small intestinal mucosa were obtained. Plasma and mucosal homogenates were lipid extracted and analyzed for 3H-1,25 content. There was a rapid disappearance of 3H-1,25, from the fetal circulation and a progressive accumulation of 3H-1,25 in the maternal circulation. Plasma and intestinal mucosal content of 3H-1,25 at 4 hours were as follows:
Conclusion: Intrafetally administered 3H-1,25 crosses the placenta and is taken up by the maternal small intestine.
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Ross, R., Florer, J., Chen, M. et al. UPTAKE OF INTRAFETALLY ADMINISTERED 3H-1,25 DIHYDROXVITAMIN D3 (1,25) BY THE MATERNAL SMALL INTESTINE. Pediatr Res 21 (Suppl 4), 220 (1987). https://doi.org/10.1203/00006450-198704010-00325
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DOI: https://doi.org/10.1203/00006450-198704010-00325