Failure of hyaluronidase to alter the early course of acute myocardial infarction in pigs

Hyaluronidase can be used to reduce interstitial edema in the presence of heparin

BACKGROUND

Treatment with the hyaluronan-degrading enzyme, hyaluronidase, reduces rejection-induced interstitial edema of transplanted organs. Hyaluronidase has also been demonstrated to reduce tissue necrosis after experimentally induced myocardial infarction, but its clinical use has been limited by an observed interaction between heparin and hyaluronan. In the present work, we investigated whether it is also possible to retain the effect of the enzyme in heparinized animals.

METHODS

Day 5 after heterotopic heart transplantation, recipient rats received a 2-hour intravenous infusion of hyaluronidase, either of ovine or of bovine origin. Concomitantly, the animals received intravenous heparin, either as 2 bolus doses or as a constant infusion.

RESULTS

Both hyaluronidase preparations effective reduced the hyaluronan content as well as the water content of the rejecting cardiac grafts. The concomitant use of heparin did not hamper the positive results, neither when heparin was administered intermittently nor when it was given continuously.

CONCLUSIONS

Our results in the transplantation model clearly demonstrate that hyaluronidase can be successfully used in heparinized individuals, provided that sufficient doses of the enzyme are given.

Effects of allopurinol on myocardial ischemic injury induced by coronary artery ligation and reperfusion

The effects of allopurinol pretreatment (1 mg/ml in the drinking water for 7 days at an estimated daily dose of 75 mg/kg) on biochemical and chemical changes occurring following left circumflex coronary artery ligation (40 min) and reperfusion (60 min) were examined in pentobarbital-anesthetized rabbits. During the ischemic phase, allopurinol pretreatment provided significant preservation of cellular ATP levels and of mitochondrial ATP generation as compared with untreated animals (P less than 0.05). During the reperfusion phase, allopurinol pretreatment significantly prevented the decrease in left ventricular pressure, sodium and calcium accumulation and decreases in sarcolemmal Na+,K+-stimulated and sarcoplasmic reticulum K+,Ca2+-stimulated ATPase activities as compared with untreated animals (P less than 0.05). In contrast, the decrease in mitochondrial (azide-sensitive) ATPase during ischemia and the partial recovery during reperfusion were unaffected by allopurinol pretreatment. Our results indicate that the myocardial protective effects of allopurinol may differ mechanistically in the ischemic and reperfusion phases of injury. The fact that rabbit hearts do not contain detectable xanthine oxidase activity would seem to preclude an obligatory role of this enzyme both in the generation of myocardial ischemic/reperfusion injury and in the protective actions of allopurinol.

Hyaluronidase does not prevent deterioration of vascular functional integrity during reperfusion after no-flow ischemia in isolated rabbit hearts

Effects of hyaluronidase on myocardial water content and distribution, and on coronary vascular hemodynamics and endothelial cell transport function were assessed in isolated rabbit hearts during 3.5 hours of reperfusion after 30 minutes of global, no-flow ischemia. In nonischemic control hearts, perfusion pressure, left ventricular end-diastolic pressure, maximum +dP/dt, and intravascular clearance of radiolabeled albumin remained constant during 5 hours of continuous perfusion, while the mean-transit time and vascular into extravascular space clearance of radiolabeled albumin increased 1.5X and 2.5X baseline, respectively. During reperfusion after 30 minutes of no flow, perfusion pressure increased 53% and interstitial fluid volume increased 2-fold, while left ventricular end-diastolic pressure and maximum +dP/dt returned to control levels. The rate of intravascular clearance of radiolabeled albumin decreased 38%, and the mean-transit time and vascular-into-extravascular space clearance of albumin increased approximately 3X and 5X baseline, respectively. Hyaluronidase blocked the ischemia-reperfusion-induced increases in total water content and in interstitial fluid volume and reduced the increases in perfusion pressure and mean-transit time of radiolabeled albumin by 40% and 45%, respectively, but did not prevent the increase in albumin vascular-into-extravascular space clearance and the decrease in albumin clearance from the coronary vasculature. These findings indicate that hyaluronidase does not prevent ischemia-reperfusion-induced increases in albumin permeation of the coronary vasculature, and suggest that its protective effect on ischemic myocardium is mediated, instead, by reducing interstitial edema and vascular resistance.

Heparin inhibits bovine testicular hyaluronidase activity in myocardium of dogs with coronary artery occlusion

Bovine testicular hyaluronidase (BTH) reduces experimental myocardial infarct size and ameliorates electrocardiographic signs of ischemia. This study was done to determine if heparin, an in vitro inhibitor of hyaluronidase activity, blocks the action of BTH in the myocardium of dogs after coronary artery occlusion. BTH was administered intravenously as 5,000 NF units/kg at 0.5 and 2.5 hours after coronary occlusion. Heparin was administered intravenously as a 150-unit/kg loading dose, followed by 10 units/kg per hour i.v., beginning 15 minutes before coronary occlusion. The area of myocardial ischemia at risk was assessed by a radiolabeled microsphere technique; the area that developed necrosis was assessed by a histochemical technique. In vivo activity of BTH was assessed by a colorimetric analysis of the BTH substrate, i.e., hyaluronic acid (HA), extracted from myocardial tissue. For biochemical analysis of HA, the heart was divided into anterior myocardium, which included ischemic tissue and posterior nonischemic myocardium. The myocardial HA content of dogs treated with BTH plus heparin (anterior, 3.44 +/- 0.40 micrograms HA/mg protein; posterior, 3.69 +/- 0.33 micrograms HA/mg protein) was not significantly different from control (anterior, 3.61 +/- 0.29 micrograms HA/mg protein; posterior, 3.55 +/- 0.23 micrograms HA/mg protein). In contrast, BTH lowered myocardial HA content (anterior, 2.16 +/- 0.21 micrograms HA/mg protein; posterior, 2.08 +/- 0.14 micrograms HA/mg protein) compared with either BTH plus heparin or control groups in both anterior myocardium (p = 0.006) and posterior myocardium (p = 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of early administration of a highly purified hyaluronidase preparation (GL enzyme) on myocardial infarct size

79 patients with suspected myocardial infarction entered a randomised trial to establish the safety of early intravenous administration of a highly purified hyaluronidase preparation (GL enzyme) and to assess its effects on eventual infarct size as measured by electrocardiographic, enzymatic, and scintigraphic criteria. Of the 71 patients with infarction, 35 received GL enzyme and 36 placebo within 6 h of the onset of chest pain. GL enzyme injected into a peripheral vein produced no adverse changes in the clinical, haemodynamic, biochemical, or haematological variables studied. GL enzyme reduced precordial electrocardiographic indices of infarct size as reflected by a diminution (p less than 0.02) in the degree of both R wave loss and Q wave development. In addition, the number of leads developing pathological Q waves (N delta Q greater than or equal to 2), a sign of progression from ischaemia to necrosis, was reduced (p less than 0.05) after GL enzyme treatment. However, there were no significant differences in infarct size as measured by cumulative creatine kinase MB isoenzyme release or technetium-99m pyrophosphate scintigraphic infarct area, or in clinical outcome during the hospital stay. Interpretation of the enzymatic and scintigraphic data was complicated by chance bias in pre-treatment randomisation which resulted in more (p less than 0.05) patients with severe haemodynamic impairment (and hence probably larger infarct sizes) entering the GL enzyme group. Nonetheless, a favourable effect of GL enzyme on infarct size was demonstrated by precordial electrocardiographic QRS mapping, here each patient acts as his or her own control.

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

The mechanism for reduced myocardial ischaemic injury by hyaluronidase was studied in open chest anaesthetized dogs. Repeated coronary artery occlusions were performed and the effect of hyaluronidase (225 NF units per kg) was studied during infusion of noradrenaline 0.125 mg/kg . min. Ischaemic 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 ischaemic tissue and from the coronary sinus draining predominantly non-ischaemic tissue. Hyaluronidase reduced sigma ST and increased subepicardial and transmural blood flow in ischaemic myocardium, but flow was not significantly changed in the ischaemic subendocardium or in non-ischaemic myocardium. Hyaluronidase had no significant effect on arterio-local venous differences of oxygen, glucose, lactate or free fatty acids across the ischaemic myocardium. In conclusion, reduction of myocardial ischaemic injury by hyaluronidase can be explained by increased collateral blood flow and not by an effect on fluxes of substrates across the ischaemic myocardium.

Glycosaminoglycan metabolism following acute myocardial infarction and the effects of intravenous hyaluronidase therapy

A series of thirteen patients with acute myocardial infarction was studied. In the 12 patients heparinised on admission, there was a fall in serum hyaluronidase activity, free amino sugar and uronic acid levels. This contrasted with a rise in creatine kinase activity. In a single unheparinised patient, the hyaluronidase level rose. This suggests that necrotic cardiac tissue releases hyaluronidase. Any beneficial effects of the local release of hyaluronidase may be minimized by heparin therapy. Study of patients on a trial of intravenous bovine testicular hyaluronidase following acute myocardial infarction could detect no rise in hyaluronidase levels. This confirms previous reports that human serum inhibits bovine testicular hyaluronidase.