Relationships between prostaglandins and estrogens on the motility of isolated rings from the rat urinary bladder.

We studied the spontaneous contractile activity and the effect of inhibitors of prostaglandin synthesis on the motility of the detrusor muscle isolated from estrous and ovariectomized rats. The constancy with time of the isometric developed tension and of the frequency of contractions of preparations obtained from estrous and spayed rats were not significantly different. In addition, the basal tone was in both cases stable and comparable during the whole experiment. Indomethacin (10(-5) M) or mefenamic acid (10(-5) M) abolished the phasic spontaneous motility whereas the basal tone was significantly diminished with time, the decrement being stabilized after 30 or 40 minutes. The action of inhibitors of prostaglandin synthesis was similar in isolated rings from estrous or ovariectomized animals. Cumulative dose-response curves of PGE2, PGE1 and PGF2 alpha demonstrated that PGF2 alpha evoked contractions with less efficacy and potency than PGs of the E series in both experimental groups. The most important finding was that the dose-response curves of PGE2 and PGE1 were shifted to the right in preparations obtained from ovariectomized rats, whereas the reactivity to PGF2 alpha was similar in estrus or after ovariectomy. In spayed rats injected with 17-beta-estradiol the contractile response of the isolated detrusor to PGE1 had greater efficacy and potency than in preparations from untreated ovariectomized animals. The present findings suggest the possibility that micturition problems commonly found in menopause could be due to a diminished sensitivity to PGE associated to low estrogen levels.