[Variation in extracellular/intracellular Ca2+ does not affect tyrosine (Tyr) suppressive effect on hCG-induced progesterone production by rat corpus luteal cells in vitro].

Ovaries of immature female rats primed with PMSG-hCG were digested with collagenase-DNAase solution to obtain the corpus luteal cell suspensions. After pre-incubation for 1 h, luteal cell suspensions were then incubated with different factors for 2 h. The progesterone contents in the incubates were measured by RIA. It was demonstrated that high Ca2+/high K+/A23187 significantly enhanced both the basal or hCG-induced progesterone production by rat luteal cells. To the contrast, decreased Ca2+ concentration in medium/EGTA/verapamil had inhibitory effect on progesterone production in the presence of hCG. Tyr had suppressive effect on hCG-induced progesterone production. but not in the presence of high Ca2+/high K+/A23187. The present study suggested that progesterone production by luteal cells of rat is influenced by concentration. Yet, variation in extra/intra-cellular Ca2+ does not affect Tyr suppressive effect on hCG-induced progesterone production. It seems that progesterone production by calcium and hCG occurs through two different mechanisms.