Influence of Age on the Inotropic Response to Acute Ethanol Exposure in Spontaneously Hypertensive Rats

Abstract

Acute ethanol exposure depresses cardiac electromechanical function, whereas chronic ethanol consumption leads to the development of a specific myopathic state. Chronic hypertension and aging have similar effects in the impairment of myocardial function. However, little is known about the effects of ethanol on cardiac mechanical function in hypertension. We studied the effect of age on baseline mechanical properties and the inotropic response to clinically relevant concentrations of ethanol (18 to 71 mmol/L) using papillary muscles from spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) at 10 and 25 weeks of age. Mechanical parameters measured were peak tension developed, time to peak tension, time to 90% relaxation, and maximal velocities of tension development and tension decline. SHR exhibited elevated systolic pressure and body weight as well as cardiomegaly and hepatomegaly at 10 and 25 weeks of age. Baseline mechanical properties were similar in SHR and WKY muscles at 10 weeks, whereas at 25 weeks, SHR muscles developed less tension, and both maximal velocities of tension development and tension decline were markedly depressed. Ethanol exposure produced concentration-dependent negative inotropic effects in both groups at both ages. Ethanol (>18 mmol/L) decreased peak tension developed in both groups at 10 weeks, although higher concentrations were required at 25 weeks. The negative inotropic effect of ethanol resulted in the shortening of time to 90% relaxation in both groups at 10 weeks and was associated with a slowing of maximal velocities of both tension development and tension decline. The results suggest that aging depresses baseline mechanical properties when coupled with hypertension. In addition, the magnitude of the negative inotropic effect of ethanol was attenuated in both groups at 25 weeks of age.