Difference in the effects of verapamil on Ca(2+)-activated K+ channels of smooth myocytes of aorta and taenia coli.
In freshly dispersed taenia coli myocytes of guinea pig, verapamil decreased the whole-cell outward current during depolarization. In aortic myocytes it has the opposite effect. In cell-attached patches, verapamil increased the frequency of opening of the maxi-K+ channel of both taenia coli and aortic myocytes at the expense of the mean open time. In taenia coli myocytes, the greater frequency did not fully compensate for the reduced open time, and the overall open probability of the channel was reduced. In aortic myocytes, the increase in open frequency overwhelmed the effect of the decrease in mean open time. None of the effects could be reproduced with nifedipine or diltiazem in either cell type.
Fan
S F
SF
Department of Physiology and Biophysics, State University of New York, Stony Brook 11794.
Kao
C Y
CY
D000818:Animals; D001011:Aorta; D002118:Calcium / Q000378:metabolism; D002469:Cell Separation; D003106:Colon; D004110:Diltiazem / Q000494:pharmacology; D004594:Electrophysiology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009543:Nifedipine / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects*; D051381:Rats; D014700:Verapamil / Q000494:pharmacology*
D015221:Potassium Channels; D014700:Verapamil; D004110:Diltiazem; D009543:Nifedipine; D002118:Calcium