Effect of Inosine on Contractile Force and High-Energy Phosphates in Ischemic Hearts

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Abstract
The effects of i.v. infused inosine on myocardial contractile force (MCF) and high-energy phosphate content were studied in 17 open-chest, pentobarbital-anesthetized mongrel dogs following occlusion of small branches of the left anterior descending and circumflex coronary arteries. In 7 dogs, MCF was measured using strain gauge arches sutured in the center of the ischemic area (IMCF), in the periphery of the ischemic area (PIMCF) and in a nonischemic area (NIMCF). After the arteries were ligated and IMCF had stabilized, an infusion of 50 ml of 50 mM inosine or saline was begun at a rate of 10 ml/min. Inosine infusion produced increases in IMCF, PIMCF and NIMCF of 32, 41 and 42% of preinfusion levels, respectively. In an additional 10 dogs, ATP and creatine phosphate (CP) content of the ischemic myocardium was determined at intervals prior to and following coronary arterial occlusion, during which time inosine (n = 5) or normal saline (n = 5) was infused. The degradation of ATP or CP was not altered with inosine infusion as compared to the saline-infused group. Inosine significantly increases MCF in ischemic hearts. This augmentation in MCF is not associated with alterations in levels of ATP or CP.