Diagnosis of Ischemic Heart Disease with AMP-Catabolites. In: De Jong JW, editor. Myocardial Energy Metabolism. Dordrecht: Springer Netherlands; 1988. pp. 237-44. [DOI: 10.1007/978-94-009-1319-6_21]

Influence of heat stress on myocardial metabolism and functional recovery after cardioplegic arrest: a 31P N.M.R study

OBJECTIVE

Heat stress and induction of heat shock proteins confer protection against myocardial ischemia-reperfusion injury; however the precise mechanisms of this effect remain unknown. We investigated the influence of heat stress on metabolic and functional recovery after cardioplegic arrest, in a protocol mimicking clinical donor heart preservation.

METHODS

Langendorff perfused rat hearts in control group (C, n = 6) and heat stressed (24 h prior to experiment) group (HS, n = 6) were subjected to 4 h of ischemia at 4 degrees C following cardioplegic arrest (St. Thomas' No. 1). 31P nuclear magnetic resonance spectroscopy was used to follow changes in ATP, phosphocreatine and inorganic phosphate concentrations during the pre-ischemic, ischemic and reperfusion periods. Myocardial adenine nucleotide levels in hearts at the end of experiments and purine catabolite release in coronary effluent during reperfusion, were evaluated using high performance liquid chromatography. Mechanical function in the pre-ischemic and reperfusion periods was evaluated using an intraventricular balloon. Western immunoblotting was used to quantitate HSP70 expression.

RESULTS

Although baseline concentrations of ATP and phosphocreatine were similar in C and HS groups, the rate of high-energy phosphate depletion was attenuated during the early phase of ischemia in HS groups. On reperfusion, recovery of ATP was 10-20% greater in HS versus C groups; phosphocreatine levels also recovered better in the HS group, transiently reaching levels 40% higher in HS versus C groups. The concentrations of adenine nucleotides in hearts were significantly higher in the HS versus C groups. These changes were associated with an attenuation of total purine catabolite release in the coronary effluent in HS versus C groups. A significant improvement in relative recovery of developed pressure was shown in HS versus C groups in the post-ischemic periods.

CONCLUSIONS

Heat stress causes beneficial changes in high-energy phosphate metabolism in the rat heart subjected to cardioplegic arrest and ischemia. Improved mechanical recovery in HS versus C groups was associated with a decreased rate of high-energy phosphate depletion and increased recovery of ATP and phosphocreatine levels during reperfusion. Changes in energy metabolism may play a role in the mechanism of cardioprotection by heat stress during prolonged hypothermic cardiac arrest. rights reserved.

Liquid chromatographic evaluation of purine production in the donor human heart during transplantation

A reversed phase high performance liquid chromatographic technique is presented allowing purine catabolite determination in a whole blood extract without a prior purification step. The method was applied to determine the timing and the profile of myocardial nucleotide catabolite release during reperfusion of the transplanted human heart. Samples of arterial and coronary sinus blood collected at various times within 1 h after aortic declamping during heart or heart-lung transplantations were used for nucleotide catabolite determination. Massive release of inosine and hypoxanthine from the heart was demonstrated. Production of adenosine was also shown but there was no liberation of xanthine or uric acid. Nucleotide catabolite release was greatest in the first 5 min (coronary sinus-arterial difference = 15-20 microM), but was still significant after 30 min of reperfusion. The determination of inosine and hypoxanthine--major catabolites released--was found to be reproducible in coronary sinus blood (coefficient of variation < 10%). However, immediate protein precipitation afer blood sample collection was necessary, as rapid metabolism of both exogenous and endogenous adenosine and inosine was demonstrated.

Effect of diltiazem and its metabolites on the uptake of adenosine in blood: an in-vitro investigation

Using whole blood from man and rabbits, the effect of diltiazem, its metabolites, and other calcium antagonists on the uptake of adenosine has been described. The uptake and metabolism of adenosine was extremely rapid with a half-life in plasma of less than 30 s. Adenosine is rapidly and extensively metabolized to hypoxanthine. Metabolites of diltiazem, deacetyl diltiazem and deacetyl O-desmethyl diltiazem were considerably more potent than the parent drug. Diltiazem was one-tenth as active as verapamil, but more active than nifedipine or amlodipine. Dipyridamole was the most potent uptake-inhibitor tested (IC50 less than 1 microM), whereas the angiotensin converting enzyme inhibitor enalapril was virtually devoid of any inhibitory activities (IC50 greater than 1000 microM). The results obtained from both man and rabbit were similar.