Effects of prostaglandin E₂ and indomethacin on 25-hydroxyvitamin D₃-1α-hydroxylase activity in isolated kidney cells of normal and streptozotocin-induced diabetic rats

The effects of prostaglandin E₂ (PGE₂) (1 μM) and indomethacin (IN) (20 μM) on 1,25 dihydroxyvitamin D₃ production were studied in renal cell suspensions isolated from control, stroptozotocin-induced diabetic, and insulin-treated diabetic rats. Renal cortex cells were isolated by enzymatic digestion, and preincubated for 30 min at 37°C with the appropriate additive(s) followed by a 1 h incubation with 8 nM 25-hydroxyvitamin D₃ in serumfree medium. Radioactivity incorporated into that fraction of the cell suspension extract co-eluting with synthetic 1,25-dihydroxyvitamin D₃ on high pressure liquid chromatography was determined All animals were raised for 5 weeks on a vitamin D-deficient diet. Isolated kidney cells from vitamin D-deficient rats showed dose-dependent response of 1,25 dihydroxyvitamin D₃ production to PGE₂. Cells from control animals demonstrated a stimulatory effect of PGE₂ (P<0.05) and a suppressive effect of IN (P<0.01) on 1,24 dihydroxyvitamin D₃ production. In contrast, cells from diabetic rat kidneys failed to respond to these agents, alterations which were reversed by insulin treatment. The accumulated data suggest that depressed synthesis of 1,24 dihydroxyvitamin D₃ previously observed in the experimental diabetic rat is due, at least in part, to an impaired production and response to PGE₂-like prostaglandins.