VITAMIN-D-RECEPTOR IN IMR-90 HUMAN FIBROBLASTS AND ANTIPROLIFERATIVE EFFECT OF 1,25-DIHYDROXYVITAMIN D-3

This study examines the effect of 1,25-dihydroxyvitamin D-3 [1,25(OH)( 2)D-3], serum or forskolin on the proliferation of IMR-90 fetal lung f ibroblasts and demonstrates, for the first time, the presence of 1,25( OH)(2)D-3 receptor (VDR) in this cell line. In quiescent, subconfluent cultures neither the treatment with 100 nM 1,25(OH)(2)D-3 nor that wi th 50 mu M forskolin influenced proliferation, while a significant inc rease was observed after incubation of the cells with 10% fetal bovine serum. Either cell number, determined on growing IMR-90 human fibrobl asts after 48 or 72 h incubation with 100 nM 1,25(OH)(2)D-3 or [H-3]th ymidine incorporation (24, 48 or 72 h incubation) significantly decrea sed, while protein content per cell increased. Northern blot analysis revealed the expression of the VDR gene, the VDR mRNA bands being prom inent in 1,25(OH)(2)D-3, serum or forskolin treated fibroblasts. VDR m RNA levels slightly decreased, when growing fibroblasts were exposed t o 100 nM 1,25(OH)(2)D-3 for 48 or 72 h.