[In vivo and in vitro effects of bradykinin on the release of beta-endorphin-like immunoreactivity].

The effect of bradykinin (BK) on the release of beta-endorphin-like immunoreactivity (beta-END-LI) in rats was studied in in vivo and in vitro. Intraperitoneal injection of BK at 5 micrograms/100 g body weight resulted in a significant increase in the plasma beta-END-LI level after 15 min. BK at concentrations of 10(-12)-10(-7) M also caused dose-dependent stimulation of beta-END-LI release from the dispersed cells of the anterior pituitary of rats. On gel chromatography, the beta-END-LI released by incubation of the cells with 10(-7) M BK separated into two components; one eluted in the same positions as human beta-lipotropin and the other as human beta-endorphin. BK did not stimulate beta-END-LI release in Ca++-free medium. Addition of 10(-3) M verapamil, 10(-6) M dexamethasone or 10(-7) M somatostatin to the incubation medium inhibited BK-induced beta-END-LI release from the cells. Ouabain (10(-5) M) also stimulated beta-END-LI release, but its effect was not additive with that of BK. These results indicate that BK stimulates beta-END-LI release and that calcium ion is involved in the mechanism of this effect.