Effect of Bromocriptine Administration during Mid-pregnancy on the Ovary Function in the Pig

Summary

Plasma concentrations of prolactin, luteinizing hormone (LH), progesterone, estradiol-17β and androgens testosterone with dihydrotestosterone were determined in pregnant gilts (n = 6) administered bromocriptine (BR) from 37—42 days of pregnancy. Blood samples were daily taken at 2h-intervals from day 34 to 45 of pregnancy. BR treatment reduced (p < 0.001) prolactin secretion from 14.8 ± 0.9 ng/ml to 8.6 ± 1.1 and 5.5 ± 0.7 during the initial 1—3 and 4—6 days of treatment, respectively. Following cessation of BR treatment prolactin returned to the pre-treatment concentrations (14.5 ± 1.0). BR did not alter LH during the first 3 days of treatment but decreased LH on days 4—6 (1.5 ± 0.1 vs 2.1 ± 0.2, p < 0.05). Bromocriptine evoked a 20% increase (p < 0.05) in estradiol-17β during days 1—3 following onset of treatment, however it suppressed androgen concentrations from 10.7 + 1.2 to 5.6 ± 0.4pg/ml in the same period. Suppression of prolactin from day 37—42 with a concurrent decrease of LH from day 40—42 of gestation did not affect maintenance of pregnancy and surprisingly was associated with a temporary elevation of progesterone. We conclude that prolactin has no luteotrophic properties during midpregnancy in gilts.

Key words

Pig - Mid-pregnancy - Bromocriptine