Effects of bupivacaine and ropivacaine on the isolated human umbilical artery.
In this in vitro study on the human umbilical artery, the effects of N(omega)-nitro-L-arginine methyl ester (L-NAME), indomethacin, prazosin, yohimbine and propranolol on the responses induced by bupivacaine and ropivacaine were investigated. Arteries isolated from umbilical cords from women who did not exhibit systemic diseases, who were not on medication and who had normal full-term deliveries, were cut into spiral strips 12 x 3 mm. Strips were mounted in organ baths at 37 degrees C continuously gassed with 5% CO(2) in oxygen. The responses to the drugs were recorded isometrically on a polygraph. In the bupivacaine study, when we administered cumulative concentrations of bupivacaine (10(-9) - 10(-4) M; n = 6) on basal tonus, there was no relaxation or contraction response on the tissue. Strips were precontracted with serotonin (10(-6)M 5-HT) then bupivacaine (10(-9) - 10(-4) M) was directly administered cumulatively. In the ropivacaine group, when cumulative concentrations of ropivacaine (10(-9) - 10(-4) M; n = 6) were administered on the tissue, preconstricted with 5-HT, ropivacaine did not alter the contraction response. Ropivacaine (10(-9) - 10(-4) M) was directly administered to the bath. Though bupivacaine produced relaxation, ropivacaine produced contraction (P < 0.05). Indomethacin, prazosin, yohimbine and propranolol did not significantly alter these responses. In addition, it was demonstrated that L-NAME did not affect the relaxation responses induced by bupivacaine. Thus adrenergic receptors, nitric oxide syntenaze and prostaglandins do not appear to affect the responses induced by these two local anesthetics.
Pharmacology Department, University of Selcuk Meram Medicine Faculty, Konya, Turkey. hbkaner@hotmail.com
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