Expression of opioid genes in bovine seminal vesicles.

In seminal vesicles, the organ producing most of seminal plasma in the bovine species, the pro‐opiomelanocortin and the proenkephalin genes are transcribed and translated, and their translation products processed into opioid peptides, which are secreted into the seminal plasma. By using a micro‐organ preparation of seminal vesicles we found that, after 20 h of incubation with labelled methionine, a multiplicity of opioids was produced. Among these, [Met]enkephalin and β‐endorphin were positively indentified, whereas in the newly formed secretion only [Met]enkephalin was detected. This may be correlated to the finding that the concentration of β‐endorphin in an extract of seminal plasma was one order of magnitude lower than that of [Leu]enkephalin and [Met]enkephalin. These findings expand the picture of the presence of opiod peptides in the male reproductive tract, indicating that they should have a role(s) in the physiology of reproduction, not only in the hypothalamus‐pituitary‐gonad...