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 non-pregnant rats. The ability of continuously infused epinephrine in high concentration (10(-6) g/ml, 30 min) to suppress spontaneous contractions due to activation of P-adrenoceptors progressively decreased, which was associated with receptor desensitization. Histidine in a concentration of 3x10(-11) g/ml had no effect, while in concentrations of 3x10(-8), 3x10(-7), and 3x10(-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.