Effect of PAF-acether on the reactivity of the isolated rat myometrium

In non-pregnant rat isolated uterine strips PAF-acether (1-100 nM) produced contractile effects on 74% of the preparations tested which were concentration-dependent in 44% of the cases (EC50 = 28 nM). All the preparations tested exhibited contractile responses to either acetylcholine or potassium. PAF-acether was less potent on myometrial strips from pregnant animals (EC50 = 0.3 microM) and was only effective on 24% of the preparations tested. A second contractile concentration-response curve was reproducible in only 14% of the preparations from non-pregnant rats (EC50 = 13 nM), whereas all strips from pregnant animals were completely refractory to a second challenge with PAF-acether. These results indicate that PAF-acether induces contraction of the isolated rat myometrium within the same range of concentrations at which it is active in other tissues.