Stimulation of Phospholipid Labeling and Steroidogenesis by Luteinizing Hormone in Isolated Bovine Luteal Cells*

Abstract

The present study was conducted to examine the effect of LH on phospholipid metabolism in corpora luteal tissue. Collagenase-dispersed cells obtained from bovine corpora lutea of early pregnancy were incubated with ³²PO₄ in the presence or absence of LH and examined for their ability to incorporate this label into phospholipids. LH (1 μg/ml) significantly increased ³²P incorporation into total lipid extracts, with a time course similar to that of progesterone synthesis. This stimulation of ³²P incorporation was dependent on the concentration of LH, and this dose-response relationship correlated well with the dose response of LH-induced progesterone production. Bovine serum albumin and ACTH had no apparent effect on ₃₂P incorporation into phospholipids or progesterone production. Separation of luteal cell phospholipid extracts by thin layer chromatography revealed that LH stimulated the incorporation ³²P₄, mainly into pho phatidic acid and phosphatidylinositol, with small increases occurring in the polyphosphoinositide fraction. The LHinduced labeling of these individual phospholipids also appeared to be temporally and dose-related to the LH-induced increases in progesterone synthesis. LH had no effect on the labeling of phosphatidylcholine, phosphatidylserine, sphingomyelin, or cardiolipin. These results indicate t at LH has selective effects on phospholipid metabolism in bovine luteal cells which may be a part of the mechanism of action of LH on steroidogenesis.