Quantitated release of different enzymes in patients with acute myocardial infarction (AMI) compared to enzyme content of human myocardium

66 QUANTITATED RELEASE OF DIFFERENT ENZYMES IN PATIENTS WITH ACUTE MYOCARDIAL INFARCTION (AMI) COMPARED TO ENZYME CONTENT OF HUMAN MYOCAHDIUN. G.M. Willems and W.Th. Hermens. Department of Biophysics, State University of Limburg, Maastricht, The Netherlands. The application of enzymatic infarct quantitation is presently questioned by the results of several authors who demonstrated incomplete recovery of enzyme depleted from the heart after experimental infarction in the dog. In this study plasma activity curves of the enzymes phosphohexose isomerase (PHI), creatine kinase (CK) and aspartate aminotransferase (AST) are related to the same curve of a-hydroxybutyrate dehydrogeduring the early phase of ennase (HBD) obtained from the same patient, zyme release after AMI. It is concluded that the release f(t) of the mentioned enzymes runs parallel to the release fHBD(t) of HBD, i.e. f(t) = the proportionality constant p equals the ratio of pfHBD(t). btoreover, myocardial tissue content of both enzymes. The values of the clearance rates k of PHI, CK and AST and the interindividual variation observed in k and p is discussed.

CHARGE STOICHIOMETRY DURING RESPIRATION TRANSPORT IN CARDIAC MITOCHONDRIA. A. Institute, University of London, 2, Beaumont Street,

DEPENDENT J. Williams, London, WIN

CALCIUM Cardiothoracic 2DX, England.

Simultaneous measurements of oxygen consumption, proton movements and calcium ion movements have been made during respiration supported calcium transport by isolated cardiac mitochondria. Calcium transport into previously de-energized mitochondria was initiated by adding potassium succinate to give a final concentration of 2.4 mM. The addition of the respiratory substrate brought about increased oxygen consumption and a calcium, proton exchange reaction. When N-ethyl maleimide WCIS included to prevent phosphate-hydroxyl exchange or phosphate-proton co-transport, a strict stoichiometric relationship was observed with one calcium ion entering the mitochondria in exchange for two protons. This stoichiometry was found to hold over a wide mnge of starting free calcium concentrations and suggests an electroneutml exchange of ejected protons for calcium ions. These results support the theory that calcium is transported into respiring cardiac mitochondria by an electrogenic process with each calcium ion carrying two positive charges. (This

work

was

supported

by

a grant

from

the

Medical

Research

Council).