Effects of noradrenaline and heparin on outward current in single smooth muscle cells of the guinea-pig vas deferens.
A transient outward current (Ito) was elicited by depolarization in single smooth muscle cells isolated from guinea-pig vas deferens under whole-cell voltage-clamp conditions. The peak amplitude of Ito was markedly decreased by over 80% within 10 s after application of 10 microM noradrenaline. When the pipette solution contained low molecular weight heparin (0.3-5 mg/ml), the inhibitory effect of 10 microM noradrenaline on Ito was apparently reduced. Our results strongly suggest that the noradrenaline-induced suppression of Ito is an event subsequent to Ca2+ release and depletion of available Ca2+ stored in the sarcoplasmic reticulum (SR) by myo-inositol 1,4,5-trisphosphate (InsP3), an event which is blocked by low molecular weight heparin.
Takeda
M
M
Department of Chemical Pharmacology, Faculty of Pharmaceutical Sciences, Nagoya City University, Japan.
Imaizumi
Y
Y
Watanabe
M
M
D000818:Animals; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D006495:Heparin, Low-Molecular-Weight / Q000494:pharmacology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D009638:Norepinephrine / Q000008:administration & dosage / Q000494:pharmacology*; D011188:Potassium / Q000502:physiology; D014649:Vas Deferens / Q000187:drug effects* / Q000502:physiology
D006495:Heparin, Low-Molecular-Weight; D011188:Potassium; D009638:Norepinephrine