Responsiveness of vitamin D-deficient fetal rat limb bones to parathyroid hormone in culture.

Radii and ulnae from 19-day fetal rats from normal or vitamin D-deficient mothers were treated with 25-hydroxyvitamin D3, 1,25-dihydroxyvitamin D3, or parathyroid hormone in vitro. Both sets of bones resorbed in response to all three agents. Statistical analysis indicated a purely additive model for the effects of vitamin D status and the bone-resorbing agents, with no evidence for interaction. The results suggest that the impaired calcemic response to parathyroid hormone seen in vitamin D-deficient animals in vivo is not the result of a specific unresponsiveness of vitamin D-deficient bone to parathyroid hormone.