SITE OF 1-ALPHA,25-DIHYDROXYVITAMIN-D3 PRODUCTION IN PREGNANCY

Metabolism of 25-hydroxyvitamin D3 (25-OH-D3) in pregnancy was investigated in vitro in New Zealand White rabbits fed a rabbit chow. Kidney homogenates from pregnant mothers and fetuses were separately incubated with [3H]-25-OH-D3. The homogenates from fetuses produced significant amounts of [3H]-1α,25-dihydroxyvitamin D3 [1α,25-(OH)2-D3] from its precursor, while those from mothers predominantly produced [3H]-24,25-dihydroxyvitamin D3 [24,25-(OH)2-D3]. The identity of the radioactive metabolites produced from [3H]-25-OH-D3 was established by periodate cleavage and comigration with synthetic 1α,25-(OH)2-D3 or 24,25-(OH)2-D3 on high pressure liquid chromatography. These results clearly indicate that the fetal kidney is at least one of the sites of 1α,25-(OH)2-D3 synthesis in pregnancy. © 1979.