PRETREATMENT WITH TRIMETAZIDINE INCREASES SARCOLEMMAL MECHANICAL RESISTANCE IN REOXYGENATED MYOCYTES

Objective: Cytoskeletal and sarcolemmal fragility secondary to anoxia may contribute to sarcolemmal rupture and cell death during reoxygenat ion of cardiomyocytes. This study investigated the influence of trimet azidine (TMZ), a drug with effects on lipid metabolism and cell membra nes, on reoxygenation-induced sarcolemmal rupture. Methods: Isolated a dult rat myocytes were submitted to 60 min of metabolic inhibition and 5 min of hypo-osmotic reoxygenation to simulate reperfusion edema in situ. Cells were allocated to 3 groups of treatment: in one group TMZ 100 mu mol/l was added to both the metabolic inhibition and reoxygenat ion buffers (group TMZ); another group was submitted to the same treat ment but cells had previously been incubated with TMZ 100 mu mol/l for 3 h (group TMZ-Pre); a control group underwent metabolic inhibition a nd hypo-osmotic reoxygenation without any treatment. Cell morphology w as monitored throughout the experiment and sarcolemmal integrity was a ssessed by quantification of LDH activity and trypan blue exclusion te st. Results: After 60 min of metabolic inhibition most cells (83.1 +/- 2%) presented rigor contracture without between-group differences. Re oxygenation resulted in hypercontracture of 84.2 +/- 2.3, 91.2 +/- 1.4 and 84.1 +/- 2.1% of cells in TMZ, TMZ-Pre and control groups, P = NS . The trypan blue exclusion test revealed a higher proportion of cells with sarcolemmal integrity in TMZ and TMZ-Pre groups than in controls (12.7 +/- 2.0, 10.0 +/- 1.5 and 6.3 +/- 0.8%, respectively, P = 0.002 ). No between-group differences in LDH activity in the extracellular m edium were observed at the onset or at the end of metabolic inhibition . However, LDH release was significantly lower (P = 0.002) in the TMZ- Pre group (1.6 +/- 0.1 IU/1000 cells) than in the TMZ and control grou ps (1.9 +/- 0.2 and 2.2 +/- 0.1 IU/1000 cells). Conclusion: Preincubat ion of cardiomyocytes with TMZ does not prevent rigor contracture indu ced by metabolic inhibition or hypercontracture during subsequent reox ygenation, but does improve sarcolemmal resistance to reoxygenation-in duced mechanical stress. This could help to explain the beneficial eff ect of TMZ on infarct size.