ACTIVITY OF PHOSPHOLIPASE-C IN OVINE LUTEAL TISSUE IN RESPONSE TO PGF2-ALPHA, PGE2 AND LUTEINIZING-HORMONE

Four ewes were utilized to determine the effects of prostaglandin (PG) F2-alpha, PGE2 and luteinizing hormone (LH) on activity of phospholipase C (PLC) in ovine luteal tissue. Corpora lutea were collected on d 10 post-estrus and six slices from one corpus luteum from each ewe were pre-incubated with [H-3]-inositol prior to incubation with one of 6 treatments. Treatments were 1) control, 2) PGF2-alpha (100 ng/ml), 3) PGE2 (10 ng/ml), 4) LH (10 ng/ml), 5) PGF2-alpha + PGE2-alpha + LH. Phospholipase C was determined indirectly by measuring the accumulation of [H-3]-inositol mono-, bis- and tris-phosphates (IP, IP2, IP3). Effects of PGF2-alpha (0 vs. PGF2-alpha) and luteotropic treatment (0 vs. PGE2 vs. LH) and their interactions were determined by analysis of variance. There was a significant main effect of PGF2-alpha (P < .001) as concentrations of IP, IP2, IP3 and total [H-3]-inositol phosphates were greater in tissue slices treated with PGF2-alpha, regardless of luteotropic treatment. Within groups receiving no PGF2-alpha (1,3,4), no effect of luteotropic treatment was observed. Within groups receiving PGF2-alpha (2,5,6), LH caused a significant (P < .05) increase in the accumulation of total [H-3]-inositol phosphates. Thus, PGF2-alpha can stimulate the activity of PLC in ovine luteal tissue and LH can potentiate this effect.