LENGTH-TENSION RELATIONSHIPS IN THE NONPREGNANT AND PREGNANT RAT UTERUS AND THE EFFECT OF ANTIPROGESTIN

Length-tension relationships and the tissue composition of the corpus and the cervix uteri were investigated in a rat model. Four groups of rats were used: nonpregnant (n = 12); day 18 of pregnancy treated with vehicle (n = 8); day 18 of pregnancy treated with the antiprogestin Z K 98 299 (Onapristone(R)) for 19 h (n = 8); and day 22 of pregnancy du ring spontaneous labour (n = 8). Increased extensibility and maximal c ontractility in both corpus and cervix uteri were demonstrated with in creased gestational age. The collagen concentration was reduced signif icantly in corporal preparations from pregnant rats compared with thos e from nonpregnant rats but not in specimens from the cervix. Antiprog estin treatment tended to increase the contractile ability.