The effect of insulin on in vitro progesterone production of human granulosa cells.

Insulin appears to play an important role in regulating ovarian function in some mammals. The present study assessed the effect of insulin on progesterone production by human granulosa lutein (G-L) cells in vitro. G-L cells were isolated from individual follicles at the time of laparoscopy for oocyte retrieval in patients undergoing in vitro fertilization/embryo transfer (IVF/ET). G-L cells were purified and plated for culture. Control wells contained no additions, while insulin was added to test wells. Although G-L cells obtained from follicles which contain an oocyte that subsequently fertilizes in vitro produce more progesterone at three and six days of culture than G-L cells from follicles that contain an oocyte that does not fertilize in vitro, insulin is unable to increase further the progesterone production of G-L cells from follicles containing either fertilized or nonfertilized oocytes at days 3 and 6 in culture. Further analysis based on the stimulation protocol (follicle stimulating hormone, n = 13; clomiphene citrate/hMG, n = 19; hMG, n = 10) also failed to yield a significant difference in basal or insulin-stimulated progesterone secretion after three or six days in culture. The lack of an effect of insulin on progesterone production by G-L cells in vitro may indicate that these cells are maximally stimulated following hyperstimulation and cannot increase progesterone production further, or may signify that insulin has no effect on the in vitro luteinization of human G-L cells obtained from hyperstimulated cycles.