| The first step of recording calcium channel current of cardiomyocytes with patch clamp technique is dissociation of myocytes. A modified enzymatic dispersion method was introduced to isolate rat left ventricular myocytes by retrograde aorta perfusion. The results showed that yield of cardiomyocytes with classic performance was from 5% to 80% and some of myocytes were calcium-tolerant.An inward current was recorded in normal rat cardiomyocytes using whole-cell patch clamp technique, which can be confirmed as L-type calcium current according to its electrophysiological properties and effect of nifedipine. Run-down refers to a phenomenon that whole cell current decreases progressively. Run-down can be slowed greatly when the ATP and GTP are added to the pipette solution.Left ventricular hypertrophy, occurs frequently in renal failure patients, usually develops to heart failure and is the main cause of death, but the electrophysiological studies of secondary left ventricular hypertrophy are inadequate. We recorded the L-type calcium current changes of cardiomyocytes from 5/6 SNx rats and felodipine intervened 5/6 SNx rats using patch clamp technique. Furthermore, The voltage dependence of Ca2+ current inactivation was examined. Theresults showed the amplitude of L-type calcium current significantly increased in 5/6 SNx rats and was blocked by felodipine partly. A negative shift of the steady-state inactivation curve was observed in 5/6 SNx rats and felodipine did not reverse this shift.A low voltage activated inward current was gained by subtracting the current recorded when hold potential was -40mV from the current recorded when hold potential was -80mV in cardiomyocytes of 5/6 SNx rat, which was absent in control. The low voltage activated current resembles T-type calcium current, suggesting the electrophysiological changes of hypertrophied cardiomyocytes may indicate some transformations such as expressions of fetal genes and regulations of cell growth in hypertrophied left ventricle.
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