Beta-endorphin in sows during late pregnancy: effects of cloprostenol and oxytocin on plasma concentrations of beta-endorphin in the jugular and uterine veins.
Beta-endorphin was measured in the plasma of pigs during late pregnancy and at different stages of the oestrous cycle. In pregnant animals, beta-endorphin secretion from uteroplacental tissues into the maternal circulation and the possible effects of oxytocin and the prostaglandin F2 alpha (PGF2 alpha) analogue cloprostenol on beta-endorphin release were determined. Plasma beta-endorphin concentrations in pregnant sows were significantly higher than in non-pregnant pigs. However, there were no significant changes in beta-endorphin values throughout the oestrous cycle. Because the increase in plasma beta-endorphin concentrations had occurred before luteolysis and onset of labour it could not be attributed to the stress of parturition. The surgical intervention of a laparotomy increased beta-endorphin release into peripheral plasma. Cloprostenol but not oxytocin caused an immediate increase in plasma beta-endorphin concentrations. At parturition, endogenous PGF2 alpha may be involved in the regulation of beta-endorphin secretion. Concentrations of beta-endorphin in the jugular and uterine vein plasma were not significantly different, and so it would appear that beta-endorphin in the plasma of pregnant sows is not of uteroplacental origin. In conclusion, changes in the concentration of beta-endorphin in peripheral plasma, associated with pregnancy but not the oestrous cycle, exist in pigs. Hence a physiological function of peripheral opioid peptides in the periparturient sow is feasible.
Aurich
J E
JE
Klinik für Geburtshilfe und Gynäkologie des Rindes, Tierärztliche Hochschule, Hannover, Germany.
Dobrinski
I
I
Parvizi
N
N
D000818:Animals; D003008:Cloprostenol / Q000494:pharmacology*; D004971:Estrus / Q000097:blood; D005260:Female; D007601:Jugular Veins; D010121:Oxytocin / Q000494:pharmacology*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000097:blood*; D011374:Progesterone / Q000097:blood; D013552:Swine / Q000097:blood*; D014599:Uterus / Q000098:blood supply; D001615:beta-Endorphin / Q000097:blood*
D003008:Cloprostenol; D011374:Progesterone; D010121:Oxytocin; D001615:beta-Endorphin