The regulation of 24,25-dihydroxyvitamin D3 production in cultures of monkey kidney cells

Primary kidney cell cultures from normal rhesus monkeys were used to study the regulation of 24,25-dihydroxyvitamin D3 production. Kidney cells were grown to confluency in the modified National Cancer Institute Medium NCTC 135 with 2% fetal calf serum and then maintained in a serum-free medium (2% bovine serum albumin) for five additional days prior to a study of regulation. Morphologically, 80% of the cultured cells were epithelial in nautre. These cells produced 24,25-dihydroxy-[3H]vitamin D3 from 25-hydroxy-[3H]-vitamin D3. The identity of the 24,25-dihydroxy-[3H]vitamin D3 was established by Sephadex LH-20 chromatography, by co-chromatography with authentic 24,25-dihydroxyvitamin D3 on high pressure liquid columns, and by periodate sensitivity. Bovine parathyroid hormone at a level of 3 U/ml or human 1-34 parathyroid hormone at 0.05 U/ml for five days suppressed 24,25-dihydroxyvitamin D3 production. Nonradioactive 1,25-dihydroxyvitamin D3 (13 pmol/ml) added once every two days for eight days led to a 2-fold increase in production of 24,25-dihydroxyvitamin D3. Exposure of renal cells to 3 mM instead of 1 mM calcium led to a marked increase in 24,25-dihydroxyvitamin D3 production. These results suggest that renal cell cultures may be an important new approach to a study of regulation of the vitamin D renal hydroxylases.