The role of lipoproteins in steroidogenesis by human luteinized granulosa cells in culture.
Progesterone secretion by primary cultures of luteinized human granulosa cells was markedly reduced when the cells were incubated in lipoprotein-deficient medium. Addition of LDL, but not HDL3, to cells cultured in lipoprotein-deficient medium stimulated progestin secretion. The effects of LDL were dose-dependent and saturable (Km = 5.5 micrograms LDL protein/ml). LDL also stimulated [3H]-oleate incorporation into cellular sterol esters, with half maximal stimulation occurring at LDL concentrations of 10 micrograms protein/ml. The cultured cells bound and internalized [125I]-LDL in a dose dependent and saturable manner (Km = 5-10 micrograms LDL protein/ml). [125I]-LDL uptake was specific in that unlabeled LDL, but not unlabeled HDL3, competed with labeled LDL for uptake [125I]-HDL3 was also taken up by the cells, but by a lower affinity mechanism. We conclude that luteinized human granulosa cells utilize LDL-carried cholesterol for progestin synthesis, and that LDL is taken up via a specific, high affinity process.
D001692:Biological Transport; D002478:Cells, Cultured; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology*; D006107:Granulosa Cells / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D008074:Lipoproteins / Q000502:physiology*; D008075:Lipoproteins, HDL / Q000502:physiology; D053440:Lipoproteins, HDL3; D008077:Lipoproteins, LDL / Q000502:physiology; D007986:Luteinizing Hormone / Q000494:pharmacology*; D011374:Progesterone / Q000096:biosynthesis* / Q000378:metabolism
D008074:Lipoproteins; D008075:Lipoproteins, HDL; D053440:Lipoproteins, HDL3; D008077:Lipoproteins, LDL; D011374:Progesterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone