PGE 1 or PGE 2 not LH Regulates Secretion of Progesterone in Vitro by the 88-90 Day Ovine Corpus Luteum of Pregnancy

Abstract

Secretion of progesterone in vitro by mature day 8 ovine corpora lutea (CL) of the estrous cycle was increased linearly by ovine LH (1, 10 and 100 ng/ml) or prostaglandin E 2 (PGE 2) 1, 10 and 100 ng/ml) in a dose dependent manner (P ≤ 0.05). Progesterone secretion in vitro by 88–90 day ovine CL of pregnancy was not affected P ≥ 0.05 by LH (1, 10 and 100 ng/ml) while prostaglandin E 1 (PGE 1) 1, 10 and 100 ng/ml) increased (P ≤ 0.05) secretion of progesterone in a dose dependent manner and PGE 2 (1, 10 and 100 ng/ml) increased (P ≤ 0.05) secretion of progesterone only at the 100 ng/ml dose. Day 8 ovine CL of the estrous cycle did not secrete (P ≥ 0.05) detectable quantities of prostaglandin F 2α (PGF 2α) or prostaglandin E (PGE) while 88–90 day ovine CL of pregnancy secrete PGE (P ≤ 0.05) but not PGF 2α (P ≥ 0.05). Regulation of PGE secretion by 88–90 day ovine CL of pregnancy may be via pregnancy specific protein B (PSPB), which increased (P ≤ 0.05) PGE and progesterone but not PGF 2α (P ≥ 0.05) secretion. Secretion of progesterone by CL of 88–90 days of pregnancy was not affected by IGF 1, IGF 2, PAF-16, PAF-18, oxytocin, PGI 2, PGD 2 or leukotriene C 4 (P ≥ 0.05). It is concluded that PGE 1 or PGE 2 but not LH regulates secretion of progesterone in vitro by 88–90 day ovine CL of pregnancy. In addition, it is concluded that 88–90 day ovine CL of pregnancy secretes it's own luteotropin, which is PGE. Secretion of PGE by ovine CL of pregnancy may be regulated by PSPB.