Comparison of tocol_ytic effects induced by ritodrine and nicardipine in ovariectomised rat treated with ist-rogen and progesterone

An in vitro sıudy was designed carry out a corn-parative suni]; ta show the antagonistic effect of ritodrine and nicardipine against acetylcholine-, o.xytocin- and INCI-induced contractions in isolated t-at uterus, treated with hormones estrogen or estrogen and progesterone. ln control groups rats were treated with 1 nıglkg est-radiol benzoat 24 hrs. prior ta excision of uterus. On the other hand. the trial group of reis were ovariectomised 9. - 12. davs before estradiol benzoat treatment and tü the sanıe group of rats estradiol benzoat plus progesteron was administered between 13. - 16. clays. The two horns of the ııterus were placed irı isolated organ baths containing de Jalon solution maintained at 37 'C and aerated with 95 % and 5 % CO2 gas mixture. In both control and ovariectomized rats, pD2 values of aceıyicholitıe were not statistically significant. The in-hibirion induced by ritodrine and nicardipine (10-8, 10-7, 10.-" M) in the contractions initiated by acerylcholine was evaluated. Ritodrine was Pim(' ta be more effective on the trial group. Mat-imal percent relaxations caused by ri-todrine and nicardipine were similar in the preparations precontracted by submaximal concentration of acetyl-eholine (3.10-5 Al'). In trial group IC50 and t112 values of ritodrine and nicardipine were than those of control groııps. The inhibition of orytocin-induced contractions by ri-todrine and nicardipine was more protıounced in trial group than control group. Similarly, the inhibition of KCI-induced contraction by nicardipine was clearly more ef-fective on trial group. Results showed that acetyicholine- and oxytocin-induced contractions were antagonized more ellectively by ritodrine in trial group. Tvvo dijferent hormonal tre-anwents did not affect nicardipine-acetylcholine in-teraction, however, oxvtocitı- and KCI- induced cont-ractions were Inhibited by nicardipine more clearly irt control group. Furthermore, in trial groups the inhibitory effect of nicardipine orz oxytocin-induced contractions was greater thall those of ritodrine.