In vitro production of 1,25-dihydroxyvitamin D3 by rat placental tissue.

Weanling female rats were fed a vitamin D-deficient diet for 4 months until they reached maturity. They were mated with normal, vitamin D-replete male rats and, at 20 days of pregnancy, the female rats were killed and their placentae were removed, homogenzied, and incubated with 25-hydroxyvitamin D3. The incubation mixtures were extracted and the extracts were subjected to Sephadex LH-20 column chromatography followed by high-pressure liquid chromatography. The 1,25-dihydroxyvitamin D3 region of the high-pressure liquid chromatogram was recycled to purity and the structure of the product was identified as 1,25-dihydroxyvitamin D3 by ultraviolet absorption spectrophotometry and by mass spectrometry. Thus it is now evident that placenta, in addition to renal tissue, is capable of converting 25-hydroxyvitamin D3 to the hormonal form of vitamin D, 1,25-dihydroxyvitamin D3.