STIMULATION OF EPIDERMAL PROLIFERATION IN MICE WITH 1-ALPHA,25-DIHYDROXYVITAMIN D-3 AND RECEPTOR-ACTIVE 20-EPI ANALOGS OF 1-ALPHA,25-DIHYDROXYVITAMIN D-3

The effects of 1 alpha;25-dihydroxyvitamin D-3 (1 alpha,25-(OH)(2)D-3) and receptor-active 20-epi vitamin D analogues (MC 1288, 20-epi-1 alpha,25-(OH)(2)D-3; MC 1301, 20-epi-24a-homo-26,27-dimethyl-1 alpha,25-(OH)(2)D-3, and KH 1060: 20-epi-22-oxa-24a-homo-26,27-dimethyl-1 alpha,25-(OH)(2)D-3) on epidermal proliferation in mice were studied in vivo. Single topical applications of ail compounds induced epidermal proliferation in a dose-dependent manner. The relative potencies in vivo (KH 1060 > MC1301 > MC1288 > 1 alpha,25-(OH)(2)D-3) correlated well with the known activities of these compounds to inhibit U 937 cell proliferation in vitro. Vitamin D-3 and 1 beta,25-(OH)(2)D-3, two compounds that do not bind the vitamin D receptor, did not affect epidermal proliferation. Our study shows that vitamin D-3 compounds that bind to the vitamin D receptor stimulate epidermal proliferation in mice.