Effects of RU486 on progesterone secretion by human preovulatory granulosa cells in culture.

The effects of RU486 on progesterone synthesis were studied in human preovulatory granulosa cells in culture. No effect was observed at 1 and 10 micrograms/mL, but at 100 micrograms/mL, RU486 inhibited the simulation of progesterone secretion induced by LH and cAMP. It is suggested that the main target of RU486 is the cytochrome P450scc function [catalyzing the formation of pregnenolone (D5P) from cholesterol], since no accumulation of D5P or hydroxy derivatives of progesterone was observed.

Evidence for the activation of phospholipases during acrosome reaction of human sperm elicited by calcium ionophore A23187.

Incubation of washed human sperm with [3H]- or [14C]arachidonic acid allowed a major incorporation of the label into phospholipids, provided that the final concentration of the fatty acid did not exceed 20 microM. A further challenge with calcium ionophore A23187 of spermatozoa suspended in a calcium-containing medium led to phospholipid hydrolysis, which could account for 10-12% of total cell radioactivity. Degradation products were identified as free, unconverted arachidonic acid, occurring with some diacylglycerol.

Phospholipase C from human sperm specific for phosphoinositides.

Human sperm lysates were incubated in the presence of 1-[14C]stearoyl-2-acyl-sn-glycero-3-phosphocholine, 1-[14C]stearoyl-2-acyl-sn-glycero-3-phosphoethanolamine or 1-[14C]stearoyl-2-acyl-sn-glycero-3-phosphoinositol. Only the latter substrate was hydrolyzed to a significant extent, with a concomitant formation of 1-[14C]stearoyl-2-acyl-sn-glycerol. Furthermore, incubation of phosphatidyl[3H]inositol under the same conditions was accompanied by the formation, in roughly equal amounts, of [3H]inositol 1-phosphate and [3H]inositol 1:2-cyclic monophosphate.

High density lipoprotein and low density lipoprotein utilization by human granulosa cells for progesterone synthesis in serum-free culture: respective contributions of free and esterified cholesterol.

Human preovulatory granulosa cells cultured in serum- and gonadotropin-free medium secreted progressively less progesterone as time elapsed. Addition of purified high density lipoproteins (HDL) as well as low density lipoproteins [very low density (VLDL) plus low density lipoproteins (LDL)] restored optimal synthesis of progesterone, and HDL was as effective as VLDL + LDL. The use of cholesterol doubly labeled lipoproteins allowed calculation of the proportions of free and esterified cholesterol converted into progesterone.

Lipoprotein and phospholipid distribution in human follicular fluids.

Human preovulatory follicular fluids, obtained in the course of stimulated cycles, were analyzed for their lipid and protein compositions. By combining different methods, a single class of lipoprotein, high-density lipoprotein, was detected in all cases. The phospholipid distribution revealed an accumulation of lysophosphatidylcholine.