PMID: 1181400Oct 1, 1975Paper

Rate of onset of cardiotonic steroid-induced inotropism: influence of temperature and beat interval.

The Journal of Pharmacology and Experimental Therapeutics
M K Park, F F Vincenzi

Abstract

Isolated rabbit atria were employed to examine the rate of onset of inotropism of two glycosides (strophanthin and ouabain) and aglycones (acetylstrophanthidin and ouabagenin) under a variety of conditions of temperature and beat interval. The rate of onset of glycoside-induced inotropism was found to be highly and directly dependent on temperature between 27 and 37 degrees C at a beat interval of 10 seconds. At a beat interval of 1 second the rate of onset of glycoside effect was faster than at a beat interval of 10 seconds and was not dependent on temperature. At 32 degrees C the rate of onset of glycoside-induced inotropism was inversely related to beat interval (the faster the stimulation rate, the faster the onset). The rate of onset of aglycone-induced inotropism was not dependent on temperature at a beat interval of 1 or 10 seconds. At 32 degrees C the rate of onset of aglycone effect was not dependent on beat interval except at beat intervals of less than 1 second. Depending on experimental conditions, increased temperature and/or myocardial activity increases the rate-limiting step for the onset of effect of cardiac glycosides. Rapid myocardial activity increased, but neither moderate myocardial activity nor increased ...Continue Reading

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