Abstract: Objective To investigate the alterations of L-type calcium current (ICa,L) in abdominal aortic ligation-induced hypertrophied rat hearts and the effect of losartan on these alterations. Methods Cardiac hypertrophy was induced by abdominal aortic ligation in rats. To record ICa,L, whole-cell patch-clamp technique was used. Results Membrane capacitance was larger in hypertrophied cells (148±29 pF) than in sham-operated cells (102±14 pF, P<0.01) and losartan-treated cells (118±27, P<0.01). The maximal peak ICa,L was increased from -835±124 pA in sham-operated cells to -1404±417 pA in hypertrophied cells (P<0.01), the corresponding ICa,L density was increased from -7.5±1.8 pA·pF-1 to -10.5±2.2 pA·pF^-1 (P<0.01), while they were reduced to -956±170 pF (P<0.01) and -8.2±1.6 pA·pF^-1 (P<0.05) respectively in losartan-treated cells. The membrane potential of half maximal activation of the hypertrophied cells (-20.6±1.0 mV) shifted to more negative potentials than sham-operated cells (-15.6±1.6 mV, P<0.01) and lorsartan-treated cells (-17.4±1.0 mV, P<0.01). The slope of the activation curve of hypertrophied cells (5.7±0.4) was decreased slightly than sham-operated cells (6.4±0.5, P<0.05). The membrane potential of half maximal inactivation of hypertrophied cells (-27.6±1.9 mV) shifted to more positive potentials than sham-operated cells (-31.4±2.2 mV, P<0.05). The slope of inactivation curves were not different in the three groups. Conclusion Treatment with losartan (30 mg·kg^-1·d^-1, ig) prevented the cell enlargement and the alterations of ICa,L in abdominal aortic ligation-induced hypertrophied rat hearts.

Key words: Losartan, Cardiac hypertrophy, Patch-clamp technique, L-type calcium current