Effects of prolactin on ovarian plasmin generation in the process of ovulation.
The present study was undertaken to assess the effects of prolactin (PRL) on gonadotropin-induced plasmin generation in the in vitro-perfused rabbit ovary. The ovarian plasmin activity was determined by measuring plasmin bound to its major inhibitor, alpha 2-plasmin inhibitor (alpha 2 PI-Plm). In the first experiment, exposure to hCG enhanced ovarian alpha 2 PI-Plm generation from 1.2 +/- 0.3 ng/min/ovary in unstimulated ovaries to 2.9 +/- 0.3 ng within 2 h. The concentration of alpha 2 PI-Plm reached a maximum at 4 h and then declined. A second peak occurred 8 h after hCG administration; however, the ovarian alpha 2 PI-Plm generation without hCG was very low throughout the entire perfusion period. In the subsequent experiment, the addition of PRL(10-10(3) ng/ml) to the perfusate inhibited hCG-induced ovulation in a dose-dependent manner. Exposure to PRL at 10(3) ng/ml significantly (p less than 0.05) inhibited hCG-induced alpha 2 PI-Plm generation in ovaries throughout the entire perfusion period. Furthermore, PRL inhibited hCG-stimulated alpha 2 PI-Plm generation at 4 h after hCG administration in the perfused rabbit ovaries in a dose-dependent manner. In conclusion, PRL directly inhibits hCG-induced ovulation in rabbit ovary, at least in part, by a mechanism depending upon inhibition of the plasmin-generating system in the preovulatory follicles.
Yoshimura
Y
Y
Department of Obstetrics and Gynecology, Kyorin University School of Medicine, Tokyo, Japan.
Nakamura
Y
Y
Oda
T
T
Ando
M
M
Ubukata
Y
Y
Koyama
N
N
Karube
M
M
Yamada
H
H
D000818:Animals; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D005260:Female; D005341:Fibrinolysin / Q000096:biosynthesis* / Q000378:metabolism; D007700:Kinetics; D010053:Ovary / Q000187:drug effects / Q000378:metabolism*; D010060:Ovulation / Q000187:drug effects / Q000502:physiology*; D011388:Prolactin / Q000494:pharmacology*; D011817:Rabbits; D000979:alpha-2-Antiplasmin / Q000378:metabolism
D006063:Chorionic Gonadotropin; D000979:alpha-2-Antiplasmin; D011388:Prolactin; D005341:Fibrinolysin