Immunoreactive beta-endorphin in the genital tract and seminal plasma of the bull

Beta-endorphin is an endogenous opioid peptide, primarily synthetised by the hypothalamus and pituitary, innvolved in the regulation of reproductive activity, mainly inhibiting LH release. To investigate the relationship between beta-endorphin and reproductive function in bulls, blood and seminal plasma were collected from 20 animals, aged 10-18 months. A wide range of beta-endorphin concentration was detected in blood and seminal plasma. A strong immunostaining for beta-endorphin was found in glandular epithelium of the prostate and vesicular glands. A weak positive signal was also observed in the epithelium of the epididymid, ductus deferens ans ampulla.