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. 1991 Jun;103(2):1417–1420. doi: 10.1111/j.1476-5381.1991.tb09804.x

Negative chronotropic effect of a novel class III antiarrhythmic drug, UK-68,798, devoid of beta-blocking action on isolated guinea-pig atria.

T Yang 1, P M Tande 1, H Refsum 1
PMCID: PMC1908346  PMID: 1679359

Abstract

1. The chronotropic effects of a novel class III antiarrhythmic drug, UK-68,798, and the beta-adrenoceptor blocker, propranolol, for comparison, were studied on spontaneously beating right atria isolated from guinea-pigs in the absence and presence of increasing concentrations of isoprenaline (10(-10)-10(-4) M). 2. UK-68,798 (10(-9)-10(-5) M) decreased spontaneous atrial rate by 6-21%. Propranolol (10(-8) -10(-6) M) also had a negative but significantly smaller chronotropic effect. 3. UK-68,798 dose-dependently reduced the maximal positive chronotropic effect induced by isoprenaline, but without significantly shifting the concentration-response curve for isoprenaline in a parallel fashion. A pD'2 value of 5.88 was obtained. As expected, propranolol displayed a competitive inhibition with a pA2 value of 8.21. 4. The results demonstrate a negative chronotropic effect of UK-68,798, which is not associated with a beta-adrenoceptor blocking action. We suggest that the negative chronotropic effect is linked with potassium channel blockade and thereby the class III antiarrhythmic action of UK-68,798.

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Selected References

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