Immunoreactive vasopressin in bull seminal fluid.

Immunoreactive arginine vasopressin (irAVP) was measured in seminal fluid with and without extraction using a specific radioimmunoassay (RIA). A large fraction of irAVP was removed after extraction on octadecasilylsilica cartridges. The measured amount of irAVP corresponded to the levels found in blood plasma. Dilutions of seminal plasma extracts were parallel with the RIA standard curve. On reversed phase HPLC the extracted material coeluted with synthetic AVP. These findings suggest an identity of this immunoreactive material with intact AVP. During incubations of synthetic AVP and its analogue 8-D-arginine vasopressing (8-DAVP) in seminal plasma, immunoreactivity decreased considerably with the former peptide, while the concentration of 8-DAVP was not significantly altered.