Low affinity of the receptor for 1 alpha,25-dihydroxyvitamin D3 in the marmoset, a New World monkey.

Circulating levels of 1,25-dihydroxyvitamin D are 10-fold higher in the marmoset, a New World monkey, than in man; to assess hormone receptors, we evaluated interactions of 1,25-dihydroxyvitamin D3 with virus-transformed lymphocytes. Soluble extracts of transformed lymphocytes from humans showed hormone binding with affinity and capacity similar to that of receptors for 1,25-dihydroxyvitamin D from other human tissues. However, soluble extracts of transformed lymphocytes from the marmoset showed a strikingly lower affinity for 1,25-dihydroxyvitamin D (Kd 2.2 vs 0.27 nM in marmoset vs human) and a mildly lower binding capacity (6.9 vs 16 fmol/mg protein). A defective receptor for 1,25-dihydroxyvitamin D3 could account for resistance of target tissues to this hormone in the marmoset.