Seasonal commitment of HMGCoA reductase activity to vitellogenin production

Abstract

In female frogs (Rana Esculenta) during gametogenesis the cholesterol synthesized in the liver by 3-hydroxy-3-methylglutaryl coenzyme A reductase is mostly exported into the blood and taken up by the oocytes. In order to understand the fate of the neosynthesized cholesterol, female and male frogs and estrogenized male controls were injected with the labelled precursor14C mevalonate. In females and in estrogenized controls, mevalonate-derived radioactivity is found in a plasmatic lipoprotein that has been identified as vitellogenin by immunological detection. The increased 3-hydroxy-3-methylglutaryl coenzyme A reductase activity present in females in Fall is likely to be committed to provide cholesterol for the lipidation of this cholesterol-rich protein.