Prostaglandin E 2 opunteracts the effects of PGF 2α in indomethacin treated cycling gilts

Abstract

Twenty crossbred gilts with at least 2 consecutive estrous cycles of 18 to 21 days in length were used to study the effects of prostaglandins E 2 and F 2α (PGE 2 and PGF 2α) on luteal function in indomethacin (INDO) treated cycling gilts. Intrauterine and jugular vein catheters were surgically palced before day 7 of the treatment estrous cycle and gilts were randomly assigned to 1 of 5 treatment groups (4/groups). With exception of the controls (Group I) all gilts received 3.3 mg/kg INDO every 8 h, Groups III, IV and V received 2.5 mg PGF 2; 2.5 mg PGF 2α + 400 μg PGE 2 every 4 hr, or 400μg PGE 2 every 4 h, respectively. All treatments were initiated on day 7 and continued until estrus or day 23. Jugular blood for progesterone analysis was collected twice daily from day 7 to 30. Estradiol-17β (E 2-17β) concentrations were dtermined in samples collected twice daily, from 2 d before until 2 d following the day of estrus onset. When compared to pretreatment values, estrous cycle length was unaffected (P>0.05) in Group I, prolonged (P<0.05) in Groups II, IV and V; and shortened (P<0.05) in Group III. The decline in plasma progesterone concentration that normally occurs around day 15 was unaffected (P>.05) in Group I; delayed (P<0.05) in Groups II, IV and V; and occurred early (P<0.05) in Group III. Mean E 2-17β remained high (31.2 ± 4.9 to 49.3 ± 3.1 pg/ml) in Groups III and IV, while the mean concentrations in Groups III and V varied considerably (17.0 ± 2.0 to 52.2 ± 3.5 pg/ml). The results of this study have shown that PGE 2 will counteract the effects of PGF 2α in INDO treated cycling gilts. The inclusion of PGF 2α appeared to either stimulate E 2-17β secretion or maintain it at a higher level than other treatments.