Progestins Biosynthesis in Rats in Vivo following Infusion of Cholesterol-7 a - 3 H and Acetate-1- 14 C into Luteinized Ovaries ∗

Summary

The synthesis and secretion of progestins from cholesterol-7_a-³H and acetate-1-¹⁴C has been investigated in the rat with luteinized ovaries by retrograde infusion of precursors into vena cava. In this system “solubilized” plasma cholesterol-7_a-³H but not acetate-1-¹⁴C derived from the circulation was a major immediate precursor which could easily enter and label the “available” cholesterol pool(s) for the biosynthesis of progestins of the rat luteinized ovary. The LH and the NADPH system increased the mass and tritium activity of progesterone converted from cholesterol-7_a-³H, whereas progesterone-¹⁴C transformed from acetate-1-¹⁴C was not increased. The higher specific activities of secreted progesterone-³H derived from cholesterol-7_a-³H was found after the addition of the NADPH when compared with LH stimulated and control groups.