Vitamin D and Cartilage. II. Biological Activity of 25-Hydroxycholecalciferol and 24,25- and 1,25-Dihydroxycholecalciferols on Cultured Growth Plate Chondrocytes*

Abstract

In order to study the effect of vitamin D3 and some of its metabolites on cartilage, chondrocytes from the proliferative zone of rabbit growth plate cartilage were isolated and grown in culture. The 35SO4 incorporation into proteoglycans extracted from the cells or into macromolecules obtained after dialysis of the culture medium was evaluated in the presence of vitamin D3, synthetic 25-hydroxycholecalciferol (25-(OH)D3), 24,25- and 1,25-dihydroxycholecalciferols (24,25-(OH)2D3 and 1,25-(OH)2D3). At concentrations between 2.4 .times. 10-13 M and 2.4 .times. 10-10 M, 24,25-(OH)2D3 was stimulatory. 1,25-(OH)2D3 was also active at 2.4 .times. 10-11 M and 1.2 .times. 10-10 M concentrations. Higher concentrations of 25-(OH)D3 (2.5 .times. 10-8 M) were necessary to obtain a similar response. Vitamin D3 was inactive at concentrations raning from 10-14-10-7 M. A polar derivative was obtained after incubation of chondrocytes or cartilage tissue with 25-(OH)D3, and was presumed to be 24,25-(OH)2D3. This cartilage polar derivative was found to be equipotent to both synthetic and biosynthetic 24,25-(OH)2D3 in the cultured chondrocytes bioassay system.