diamide and Coronary-Disease

Freshly isolated adult rat heart myocytes contain total glutathione and reduced glutathione (GSH) at levels quite comparable to those in intact rat heart. Total glutathione can be depleted from 11 to 1 nmol/mg protein or less by treatment with cyclohex-2-ene-1-one without effect on either cellular ATP, rod-cell morphology or the integrity of the sarcolemma. Glutathione levels and redox state are not altered significantly when the Ca-tolerant, quiescent cells are subjected to a period of anoxia followed by reoxygenation. This oxygen paradox protocol results in irreversible hypercontracture of the contractile elements into an amorphous mass in the bulk of the cells, but little loss of sarcolemmal integrity. When the myocytes are subjected to an externally applied oxidant stress by the addition of either diamide or t-butylhydroperoxide, GSH is rapidly depleted with accumulation of oxidized glutathione (GSSG. On continued aerobic incubation both of these reagents promote a slower depletion of cellular ATP and a parallel hypercontracture. Cells treated with t-butylhydroperoxide, but not those with diamide, also generate increasing amounts of thiobarbituric acid reactive species as an indication of lipid peroxidation and show a parallel loss of sarcolemmal integrity. It is concluded that respiring myocytes and those subjected to the oxygen paradox do not produce oxygen radicals in sufficient amounts to displace the GSH/GSSG redox poise and depletion of myocyte glutathione per se is not detrimental to the short term survival of the cells. In addition, aerobic myocytes subjected to external oxidant stress can be damaged irreversibly by two pathways, a hypercontracture that correlates with depletion of ATP and a loss of sarcolemmal integrity that correlates with lipid peroxidation.

Topics: Animals; Coronary Disease; Cyclohexanones; Diamide; Glutathione; Heart; Hypoxia; Myocardium; Oxidation-Reduction; Oxygen; Peroxides; Rats; Reperfusion Injury; tert-Butylhydroperoxide

Reversal of mitochondrial dysfunction caused by uncouplers of oxidative phosphorylation, diamide, ageing and ischemia was studied using 2-mercaptopropionylglycine (MPG) in reduced and oxidized (ox-MPG) forms and other SH compounds. Rat heart mitochondria and mitochondrial ATPase, OS-ATPase from beef heart and the isolated working rat heart preparation were examined. MPG and ox-MPG partly prevented and reversed mitochondrial uncoupling and improved deteriorated heart function. ATPase activities were decreased by MPG and ox-MPG in both types of preparation. Three mechanisms are probably involved in thiol action. These comprise alternatively and/or additively: a) SH/S-S interchange reactions; b) free radical scavenger function; c) polar-polar (apolar) interactions. This may contribute to improve oxidative phosphorylation which is considered as a result of recoupling damaged mitochondria by MPG.

Topics: Adenosine Triphosphatases; Aging; Amino Acids, Sulfur; Animals; Cattle; Coronary Disease; Diamide; Female; In Vitro Techniques; Mitochondria, Heart; Rats; Rats, Inbred Strains; Sulfhydryl Compounds; Tiopronin; Uncoupling Agents