Ability of L-histidine to decrease desensitization of the myometrium to epinephrine

Experiments were performed with 62 longitudinal strips of the uterine horns from 10 nonpregnant rats. The ability of continuously infused epinephrine in high concentration (10(-6) g/ml, 30 min) to suppress spontaneous contractions due to activation of beta-adrenoceptors progressively decreased, which was associated with receptor desensitization. Histidine in a concentration of 3 x 10(-11) g/ml had no effect, while in concentrations of 3 x 10(-8), 3 x 10(-7), and 3 x 10(-6) g/ml decreased the degree of desensitization. Our results indicate that histidine not only potentiates beta-adrenoceptor activation, but also prevents the development of desensitization. These data should be taken into account during therapy with beta-adrenoceptor agonists.