Trimetazidine (S 50 16), a molecule developed by the Servier Research Institute, is a cellular anti-ischemic agent. Its chemical name is I -(2,3,4-trimethoxybenzyl)-piperazine dihydrochloride (Fig. I ). Initial pharmacological studies have indicated that trimetazidine prevents cellular changes associated with ischemia or hypoxia, but it has no effect under normoxic conditions ( I ,2).Trimetazidine is freely soluble in water (80%), sparingly soluble in methanol, but insoluble in other organic solvents. Trimetazidine solution is slightly sensitive to light although substantially less than dihydropyridines. The molecular weight of tnmetazidine is, as a dihydrochloride, 339.27 and, in basic form, 266.34. The molecule has two pKa values (4.32 and 8.95) and the pH value of an aqueous solution (5 mg/ml) is 3; this aqueous solution is stable at room temperature. PHARMACOLOGY Effects on the Hypoxic Cell and on the Ischemic TissueIschemia is defined as a deficiency of blood supply in a given tissue, and consequently of oxygen supply to the cells. Ischemia results in a decrease of oxidative metabolism that is responsible for the various functional disorders observed in the cell: reduction in the production of energetic compounds, accumulation of protons, and increase in the generation of oxygen-derived free radicals. The aggression of oxygenderived free radicals towards living tissues is therefore superimposed on the energy disorders and added to the effects of acidosis, which severely alters cellular homeostasis and results in accumulation of calcium within the cell. This considerable excess of intracellular calcium blocks all vital enzymatic functions, leading to necrosis.Despite hypoxia or induced ischemia, trimetazidine maintains homeostasis and cellular functions and inhibits cytolysis. This activity has been evidenced in vivo, by Camilleri and Joseph (3), Fitoussi et al. (4), and Catroux et al. ( 5 ) , using different models of ischemia. After induction of left ventricular infarction in the rat by coro-

Free radicals have been implicated in several aspects of cellular injury, both during ischemia and reperfusion of the myocardium. In this study, formation of free radicals in the isolated rat heart was measured a) directly using electron paramagnetic resonance (EPR) spectroscopy and b) indirectly using the generation of thiobarbituric acid reactants as an index of lipid peroxidation. EPR spectra of frozen heart powder recorded at 100 degrees K show several lines and consist of different components separated by temperature studies: signal C disappears after warming the sample 1 minute at 190 degrees K and is suggestive of a triplet signal g = 2.001, aN = 25 Gauss; signal B g parallel = 2.034, g perpendicular = 2.007, disappears after 1 min at 240 degrees K, and is similar to those previously reported for oxygen alkylperoxyl free radical; the remaining signal, signal A with g = 2.004 is identical to that of a carbon-centered ubiquinone free radical. The total free radical concentration in isolated rat heart perfused at a constant flow rate of 12 ml/min was increased by 44% compared with control (p less than 0.05) after 10 minutes of normothermic global ischemia with a 10% residual flow, and by only 31% compared with control after 20 seconds of reflow with oxygenated perfusate (p less than 0.05). Compared with the reperfused group, trimetazidine 10(-5) M administered 15 minutes before the ischemic period decreased the free radical concentration (-20%). However, this free radical generation in heart was not associated with a concomitant increase of lipid peroxides.

Specific angiotensin binding to rat hepatocytes and purified liver plasma membranes was measured by using biologically active [(3)H]angiotensin (sp. radioactivity 14Ci/mmol). The kinetic parameters for angiotensin binding to hepatocytes are: K(+1) (association rate constant). 100mum(-1).min(-1); K(-1) (dissociation rate constant), 2min(-1); K(d) (dissociation constant). 30nm; maximal binding capacity, 0.42pmol/10(6) cells or 260000 sites/cell. Angiotensin binding to membranes is profoundly affected by GTP (0.1mm) and NaCl (100mm); these regulatory compounds greatly enhance both the rate of association and of dissociation and also the extent of dissociation. K(d) amounts to 10nm in the presence of GTP+NaCl and to 1.5nm in their absence; maximal binding capacity is 0.70pmol/mg of protein, both with or without GTP+NaCl. The relative affinities of 11 angiotensin structural analogues were deduced from competition experiments for [(3)H]angiotensin binding to hepatocytes and to membranes (in the latter case, GTP + NaCl were not included, in order to study the higher affinity state of the receptor). These are highly correlated with their biological activity (activation of glycogen phosphorylase in hepatocytes). Binding to membranes occurs in the same concentration range as the biological effect. On the other hand, the existence of numerous spare receptors is suggested by the observation that binding of the agonists to hepatocytes requires 25-fold higher concentrations than those needed for their biological activity. These data clearly suggest that the detected binding sites correspond to the physiological receptors involved in the glycogenolytic action of angiotensin on rat liver.

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