Release of neurophysin I and oxytocin by stimulation of the genital organs in bulls.

Oxytocin and bovine neurophysin I (bNpI) were estimated by radioimmunoassay in jugular vein plasma which was collected continuously from 18 bulls. No release of peptides was observed during successive matings with a cow in oestrus or during successive mountings on a cow with ejaculations into an artificial vagina. Stimulation with an electro-ejaculator or, to a smaller extent, massage of the seminal vesicles and ampullae per rectum caused an increase of oxytocin accompanied by a release of bNpI.

[Plasma oxytocin levels during lactation (author's transl)].

During suckling, endogenous plasma oxytocin levels were repeatedly determined by RIA. They showed rapid fluctuations varying from 10 to 129 muU/ml. This suggests spurt releases of ocytocin of an order of magnitude of 10 to 100 mU.

Development of a radio-immuno-assay for oxytocin.

High affinity antibodies against oxytocin were produced by multiple intradermal injections. The antibodies do not cross react with lysine vasopressin. Reduction of the S-S link changes the immunoreactivity.