Cultured rat growth plate chondrocytes express low levels of 1alpha-hydroxylase.

ABSTRACT

Growth plate chondrocytes are the target of the hydroxylated vitamin D metabolites 1alpha,25(OH)2D3 and 24,25(OH)2D3. Because studies on the production of these polar metabolites were inconclusive in various in vitro systems, the expression of a potential paracrine/autocrine vitamin D system was examined in primary cultures of rat growth plate chondrocytes using real-time RT-PCR. Compared to UMR cells and renal homogenates primary cultures of growth plate chondrocytes expressed low levels of 25-hydroxy-1alpha-hydroxylase as well as 25-hydroxy-24-hydroxylase. The expression of both is modulated by 25 vitamin D3, but 1alpha,25(OH)2D3 affected only 25-hydroxy-24-hydroxylase. If these findings are confirmed in intact growth plates, the polar vitamin D metabolites could act in a paracrine/autocrine fashion within the growth plate.