Abstract
Summary
Thyroparathyroidectomized lactating rats were administered calciferol (Vit. D2) at a level of 0.2 mg/100 g BW in conjunction with 3 μg L-thyroxine/100 g BW from day 4 to 19. Milk yields determined on day 14, 16, 18, and 20 were not significantly different from the milk yield of a group of sham-operated rats but were higher than in a larger group of control animals. The litter weight of the experimental group was less than the sham-operated controls. Eight hours after operation serum Ca declined from 10.2 to 6.4 mg% but was restored to normal levels by calciferol on day 14 and 20. DNA content of the mammary glands of the two groups was similar. These data suggest that calciferol can take the place of the parathyroid hormone in mobilizing serum calcium adequate for the requirements of lactation in rats.
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