The in vitro effect of boar semen on the contractility of rat uteri.

Contradictory reports in the literature provoked the investigation of a possible oxytocic effect of boar semen on in vitro rat uterus preparations. When fresh boar seminal plasma (SP), dialyzed seminal plasma (DSP) or a filtrate of acetone-extracted seminal plasma (AE) were added to uterine preparations, both the frequency and force of spontaneous contractile activity tended to be depressed. When the uterine preparations were primed with oxytocin (1.6 USP units/100 ml bathing solution), treatment with SP and AE resulted in an increased frequency of contraction but no increase in force. DSP increased neither the frequency nor force of contractions. A solution of salts and organic compounds that approximated the small molecular or dialyzable components of boar semen ("synthetic boar seminal plasma" or BS) affected contractility in a manner similar to SP and AE. When the rat uterus was bathed in a low calcium physiological salt solution, none of the seminal treatments (SP, DSP, AE, or BS) were capable of initiating a contraction. Further, the force of carbachol-induced contractions in these uterine preparations was markedly depressed by these seminal treatments. In contrast, treatment with oxytocin nearly doubled the contractile force. The depressant effect of SP, DSP and AE on both spontaneous and carbachol-induced contractions appeared to be irreversible. Mineral analysis of SP, DSP, AE, BS and the low calcium salt solution showed the SP, AE and BS contained amounts of Ca(2+) and Mg(2+) which could have altered the uterine contractility. In addition, a non-dial-yzable factor in SP appeared to have a similar effect.