Tohoku J. Exp. Med., 1998, 184 (4)

Short Report

Isoprenaline Enhances Both Voltage-Dependent Ba2+ and K+ Currents in Guinea-Pig Vas Deferens

HACHIRO INOMATA, TOMOFUMI MIMATA1 and MAKOTO WAKUI2

College of Allied Medical Science, Akita University, Akita 010-8543, 1Department of Applied Physiology, Tohoku University School of Medicine, Sendai 980-8575, and 2Department of Physiology, Hirosaki University School of Medicine, Hirosaki 036-8562

  • In the guinea-pig vas deferens, isoprenaline (ISO) can exert significantly enhanced effects on voltage-dependent Ca2+ channel current carried by Ba2+ (IBa) via beta-adrenoceptcr activation. Voltage-dependent Ba2+ (IBa) and K+ currents (IK) were recorded in the preparation voltage-clamped in a Krebs solution replaced Ca2+ by Ba2+ (Ba2+ solution) of 36°C. At a holding potential of -40 mV, ISO markedly increased IBa evoked by depolarizing pulses, whereas it also increased IK at a holding potential of -20 mV so as to inactivate Ca2+ channel. This ISO-induced enhancement of IBa seems to be contradictory to the suppression of contraction by b-adrenoceptor activation in normal Krebs solution.
    Key words--- isoprenaline; barium current; vas deferens
    © 1998 Tohoku University Medical Press

    Tohoku J. Exp. Med., 1998, 184, 317-320
    Address for reprints: Hachiro Inomata M.D., Akita University College of Medical Science, 1-1-1 Hondo, Akita 010-8543, Japan.
    e-mail: hi1218@ipc.akita-u.ac.jp

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