Parathyroid hormone stimulates mammalian renal 25-hydroxyvitamin D3-1 alpha-hydroxylase in vitro

We have shown that parathyroid hormone (PTH) stimulates 25-hydroxyvitamin D2-1 alpha-hydroxylase activity in mitochondrial preparations of guinea pig kidney in vitro.1,25-[3H]dihydroxyvitamin D3 produced from 25-[3H]hydroxyvitamin D3 was identified by both normal phase and reversed-phase high pressure liquid chromatography. Enzyme stimulation by PTH was dose-dependent, peaked after 15 minutes of incubation with hormone and was maximal at concentrations of approximately 10(-10) M PTH-(1-84) and PTH-(1-34). This guinea pig renal model therefore permits direct examination of hormonal regulation of the mammalian enzyme in vitro.