Endocrinology, Vol 116, 2523-2527, Copyright © 1985 by Endocrine Society

ARTICLES

Diminished internalization and action of 1,25-dihydroxyvitamin D3 in dermal fibroblasts cultured from New World primates

JS Adams, MA Gacad, AJ Baker, G Kheun and RK Rude

We investigated the occurrence of 1,25-dihydroxyvitamin D3 [1,25- (OH)2D3]-resistant osteomalacia in the New World primate colony of Saguinus imperator at the Los Angeles Zoo. The mean serum concentration of 1,25-(OH)2D3 was elevated 5-fold in the New World primates compared to that in their Old World counterparts. The specific internalization of 0.6 nM [3H]1,25-(OH)2D3 by cultured dermal fibroblasts from New World primates was reduced 75% compared to that by cells from Old World primates or man. The decrease in hormone uptake resulted from a decrease in the number of high affinity intracellular binding sites for 1,25-(OH)2D3 and apparently caused a 90-95% reduction in 1,25-(OH)2D3- induced 25-hydroxyvitamin-D3-24-hydroxylase activity. There was no alteration in the capacity or avidity of New World primate serum for 1,25-(OH)2D3 compared to that of serum from Old World primates. These data suggest that the occurrence of vitamin D-resistant osteomalacia in New World primates is the result of decreased high affinity, receptor- mediated uptake of 1,25-(OH)2D3 by the target cell.

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