Effect of hyaluronidase on substrate exchange and blood flow in the ischaemic myocardium of the dog

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Abstract
The mechanism for reduced myocardial ischemic injury by hyaluronidase was studied in open-chest anesthetized dogs. Repeated coronary artery occlusions were performed and the effect of hyaluronidase (225 U/kg) was studied during infusion of noradrenaline [norepinephrine] 0.125 mg/kg per min. Ischemic injury was measured as the sum of ST segment elevations (.SIGMA.ST) at 10-15 sites. Regional myocardial blood flow was determined by tracer microspheres. Blood for metabolic studies was sampled from a local coronary vein draining ischemic tissue and from the coronary sinus draining predominantly nonischemic tissue. Hyaluronidase reduced .SIGMA.ST and increased subepicardial and transmural blood flow in ischemic myocardium, but flow was not significantly changed in the ischemic subendocardium or in nonischemic myocardium. Hyaluronidase had no significant effect on arterio-local venous differences of O2, glucose, lactate or free fatty acids across the ischemic myocardium. Reduction of myocardial ischemic injury by hyaluronidase can be explained by increased collateral blood flow and not by an effect on fluxes of substrates across the ischemic myocardium.
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