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Postnatal fall and rise of circulating 25-hydroxyvitamin D in the rat*
Insights
Neonatal rat pups experience a significant drop in plasma 25-hydroxyvitamin D levels within two weeks of birth. Levels recover by 3-4 weeks, suggesting insufficient intake or production in early life.
Area of Science:
- Biochemistry
- Neonatal Physiology
- Nutritional Science
Background:
- Vitamin D is crucial for calcium homeostasis and bone health.
- Neonatal vitamin D status is influenced by maternal supply and endogenous production.
- Understanding vitamin D metabolism in early life is vital for preventing deficiency-related disorders.
Purpose of the Study:
- To investigate the changes in plasma 25-hydroxyvitamin D concentrations in suckling rat pups.
- To determine the role of milk intake and endogenous production in maintaining vitamin D levels during early development.
- To compare vitamin D status between neonatal and weaned rats.
Main Methods:
- Measurement of plasma 25-hydroxyvitamin D levels at different ages (birth, 12 days, 3-4 weeks).
- Administration of radiolabeled 25-hydroxyvitamin D (tritium-labeled) to assess its metabolism and half-life.
- Chromatographic analysis of lipid extracts from neonatal tissues to track vitamin D metabolites.
- Intraperitoneal injection of radiolabeled 25-hydroxycholecalciferol in young and older suckling pups.
Main Results:
- Plasma 25-hydroxyvitamin D levels decreased significantly from birth (5-6 ng/mL) to 12 days of age (1-2 ng/mL) in rat neonates.
- Concentrations returned to or exceeded birth levels by 3-4 weeks of age.
- The plasma half-lives of tritium in young and older suckling pups were similar (approximately 2.9-3.0 days) after 'H-25-hydroxycholecalciferol administration.
- Tissue analysis indicated vitamin D transfer from maternal milk.
Conclusions:
- Young suckling rats exhibit a decline in plasma 25-hydroxyvitamin D, indicating insufficient levels to maintain concentrations observed at birth.
- This deficiency may stem from inadequate intake via milk or insufficient endogenous production during the early suckling period.
- Weaned rats appear to manage vitamin D levels more effectively than their younger, milk-dependent counterparts.
Abstract:
Plasma 25-hydroxyvitamin D levels (5 to 6 ng. per millilter at birth) decreased significantly at age 12 days (1to 2 ng. per millilter) in rat neonates. At 3 to 4 weeksof age, the plasma concentrations of 25-hydroxyvitamin D had risen to birth levels or higher. Chromatography of lipid extracts of neonatal tissues following in vivo administration of 'H-25-hydroxyvitamin D' from the milk of mothers who had been given 'H vitamin D' intravenously. Following intraperitoneal injection of equal (or 3-fold larger doses to older pups) doses of 'H-25-hydroxycholecalciferol, the half-lives of 'H in plasma were 2.9 to 3.0 days and 2.8 to 3.05 days in young and oldersuckling pups, respectively. These data collectively suggest that young suckling rats,unlike weaning rats, do not receive and/or produce sufficient 25-hydroxyvitamin D to maintain the blood concentration observed at birth.