Acute effects of prostaglandin F2 alpha on inositol phospholipid hydrolysis in the large and small cells of the bovine corpus luteum.

The present studies were conducted to determine whether the large or small bovine luteal cell was the site for the stimulatory effect of prostaglandin F2 alpha (PGF) on phospholipase C-catalyzed inositol phospholipid hydrolysis. Corpora lutea were removed from heifers during the luteal phase of the normal estrous cycle. Small luteal cells were isolated by unit-gravity sedimentation and large luteal cells were isolated by flow cytometry using a Becton Dickson FACS 440 cell sorter. PGF provoked rapid (5-30 s) and sustained (up to 30 min) increases in the levels of inositol mono-, bis-, and trisphosphates (IP, IP2, IP3, respectively) in small luteal cells. IP3 was formed more rapidly than IP2 or IP following PGF treatment. The PGF-stimulated increase in IP3 was accompanied by a transient reduction in the levels of 3H-labeled phosphatidylinositol 4,5-bisphosphate. LiCl (10 mM) enhanced inositol phosphate accumulation in response to PGF. Maximal increases in inositol phosphate accumulation were observed with 1-10 microM PGF and half-maximal increases were observed with 60 nM PGF. PGF (1-10 microM) had no effect on cAMP levels but stimulated small increases in progesterone accumulation in 30 min incubations of small luteal cells. PGF also increased the accumulation of inositol phosphates in large luteal cells. The increases were apparent within 5 min of incubation (the earliest time examined) and further increases were observed in incubations lasting 30 min. PGF had no significant effect on cAMP or progesterone in 30 min incubations of large cells.(ABSTRACT TRUNCATED AT 250 WORDS)