The mechanism of action of Cowper's secretion in coagulating rat semen.

In the rat, mouse and hamster, but not in the guinea-pig, Cowper's secretion reacts in vitro with vesicular secretion to produce a coagulant (Hart & Greenstein, 1968). Unlike vesiculase, the pH optimum of this reaction is acidic. In the rat, the active agent secreted by Cowper's glands that is responsible for coagulation is heat stable and non-dialysable. Electrophoretically the active molecule migrates only slightly at a pH 8\m=.\6and reacts chemically as a glycoprotein. The vesicular substrate in the rat which coagulates upon exposure to Cowper's secretion has been shown to be a protein, electrophoretically different from the substrate of vesiculase (Hart & Greenstein, 1968). Recent data suggest that vesiculase promotes vesicular coagulation by transamidase reactions (Notides & Williams-Ashman, 1967). This paper presents evidence which suggests that the mechanism by which Cowper's secretion coagulates vesicular substrate is non-enzymatic, involving, at least in part, an ionic interaction between Cowper's secretion and substrate. Cowper's secretion was obtained from mature male rats by milking the glands into a phosphate buffered solution of pH 5\m=.\9which contained 10% (w/v) ammonium sulphate. The solution was dialysed for 12 hr at 4\s=deg\C against