Stimulation of release of beta-endorphin and oxytocin by prostaglandin F2 alpha in cattle at parturition.

Concentrations of beta-endorphin and oxytocin were measured in plasma of cows before, during and after parturition. The effect of the PGF2 alpha analogue cloprostenol on beta-endorphin and oxytocin release was investigated. During parturition, there were marked, parallel increases in beta-endorphin and oxytocin concentrations. Both hormones were released in an episodic manner in conjunction with uterine and abdominal contractions. It is therefore likely that factors stimulating oxytocin release also enhance beta-endorphin secretion. This suggests a role of labour or labour-associated hormones in stimulating peripheral beta-endorphin release. Cloprostenol caused an immediate, pronounced increase in plasma beta-endorphin and oxytocin concentrations.