PARENT SESSION
BIOLOGY OF PREGNANCY AND IMMUNE FUNCTION
Harborside C
7:30 AM-10:00 AM

(331) EFFECT OF LUTEINIZING HORMONE, PREGNANCY-SPECIFIC PROTEIN B, OR ARACHIDONIC ACID ON OVINE PLACENTAL SECRETION OF PROSTAGLANDINS E₂ AND F₂.

Weems, Charles¹, Weems, Yoshie¹, Humphreys, Vanessa¹, Kim, Laurie¹, Tsuda, Vicki¹, Sasser, Garth², ¹ Dept. of Human Nutrition, Food and Animal Sciences, Honolulu, Hawaii² Dept. of Animal Science, Moscow, Idaho

ABSTRACT- Ovariectomy at days 55 or 90 does not abort ewes and half of progesterone (P₄) secretion at day 90 is from the corpus luteum (CL) and half is from the placenta. Hypophysectomy before day 50, but not after day 50, aborts ewes. PGE₂, not LH, stimulates P₄ secretion by 90 day CL of pregnancy in vitro in ewes. During pregnancy in cows and ewes, pituitary LH content, LH in blood and LH peak height and frequency decreases as pregnancy progresses, indicating the CL becomes less dependent on LH for CL P₄ secretion. Regulation of placental P₄ secretion is unknown but may be PGE₂ at day 90 in ewes. PSPB increases in blood of ewes by day 21 of pregnancy and increases further as pregnancy progresses. LH binds to cow endometrium during luteolysis and increases PGF₂ secretion in vitro. The objective was to determine the effects of LH, PSPB or arachidonic acid on ovine endometrial or placental PGE₂, PGF₂ or P₄ secretion. Days 8, 11, 13 or 15 ovine endometrium of the estrous cycle or days 8,11, 13, 15, 20, 30, 40, 50, 60 and 90 caruncle/placenta post breeding (7/group) were incubated in M-199 with Vehicle, LH, PSPB or arachidonic acid for 4 and 8 hr. Media were analyzed for PGE₂, PGF₂ or P₄ by RIA. Data were analyzed by a Factorial Design for ANOVA. LH stimulated (P<0.05) PGF₂ secretion by day 15 endometrium of the estrous cycle and by caruncles/placenta from days 15, 20, and 30 post breeding. Arachidonic acid increased (P<0.05) caruncular/placental PGE₂ secretion on days 13-60. LH increased (P<0.05) PGE₂ secretion by days 15-50 but not days 60 or 90 caruncle/placenta. PSPB increased (P<0.05) PGE₂ and P₄ secretion by 60 and 90 day placenta. It is suggested that LH regulates ovine placental secretion of PGE₂ up to day 50, while PSPB regulates PGE₂ secretion after day 50 of pregnancy.

KEY WORDS: endometrium, placenta, prostaglandins, sheep