| 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 microgram/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 concentrations 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 32PO4, mainly into phosphatidic acid and phosphatidylinositol, with small increases occurring in the polyphosphoinositide fraction. The LH-induced 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 that 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. |
