The effects of massive doses of methylprednisolone on myocardial contractility and peripheral vascular resistance

Abstract

Eleven normal dogs, nine chronically cardiac denervated dogs (four after betablockade with propranolol), and five acutely adrenalectomized and cardiac denervated dogs were studied on cardiopulmonary by-pass, at constant coronary blood flow, by means of an isovolumic left heart preparation. Methylprednisolone, in a dose of 30 mg. per kilogram of body weight, was given intravenously, and changes in myocardial contractility were assessed by measurement of left ventricular peak pressure (LVP max), peak LV dP dt , and maximum measured LV contractile element velocity (max V CE). In the normal dogs, methylprednisolone caused a significant enhancement of myocardial contractility (LVP max + 21 per cent), dP dt max + 27 per cent, and max V CE + 22 per cent, P < 0.01 in all). Chronically cardiac denervated animals showed similar effects, but with significantly greater percentage responses than the normal dogs in LVP max (+ 33 per cent) and dP dt max (+ 53 per cent), P < 0.01 in both. These changes were greatly attenuated or abolished in the denervated, beta-blocked dogs, and in the acutely adrenalectomized and cardiac denervated animals. These results confirm an acute, positive inotropic effect of methylprednisolone in vivo, and suggest that this influence is mediated indirectly by the release and/or potentiation of endogenous catecholamines.