INFLUENCE OF AGE ON THE INOTROPIC RESPONSE TO ACUTE ETHANOL EXPOSURE IN SPONTANEOUSLY HYPERTENSIVE RATS

Acute ethanol exposure depresses cardiac electromechanical function, w hereas chronic ethanol consumption leads to the development of a speci fic myopathic state. Chronic hypertension and aging have similar effec ts in the impairment of myocardial function. However, little is known about the effects of ethanol on cardiac mechanical function in hyperte nsion. We studied the effect of age on baseline mechanical properties and the inotropic response to clinically relevant concentrations of et hanol (18 to 71 mmol/L) using papillary muscles from spontaneously hyp ertensive 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 ten sion development and tension decline. SHR exhibited elevated systolic pressure and body weight as well as cardiomegaly and hepatomegaly at 1 0 and 25 weeks of age. Baseline mechanical properties were similar in SHR and WKY muscles at 10 weeks, whereas at 25 weeks, SHR muscles deve loped less tension, and both maximal velocities of tension development and tension decline were markedly depressed. Ethanol exposure produce d concentration-dependent negative inotropic effects in both groups at both ages. Ethanol (>18 mmol/L) decreased peak tension developed in b oth groups at 10 weeks, although higher concentrations were required a t 25 weeks. The negative inotropic effect of ethanol resulted in the s hortening of time to 90% relaxation in both groups at 10 weeks and was associated with a slowing of maximal velocities of both tension devel opment and tension decline. The results suggest that aging depresses b aseline mechanical properties when coupled with hypertension. In addit ion, the magnitude of the negative inotropic effect of ethanol was att enuated in both groups al 25 weeks of age.