The Alteration of Ca<SUP>2&#8290;</SUP>-activated K<SUP>&#8290;</SUP> Channels in Coronary Arterial Smooth Muscle Cells Isolated from Isoproterenol-induced Cardiac Hypertrophy in Rabbit

The Alteration of Ca<SUP>2&#8290;</SUP>-activated K<SUP>&#8290;</SUP> Channels in Coronary Arterial Smooth Muscle Cells Isolated from Isoproterenol-induced Cardiac Hypertrophy in Rabbit

<P> It has been proposed that Ca<SUP>2&#8290;</SUP>-activated K<SUP>&#8290;</SUP> (K<SUB>Ca</SUB>) channels play an essential role in vascular tone. The alterations of the properties of coronary K<SUB>Ca</SUB> channels have not been studied as a possible mechanism for impaired coronary reserve in cardiac hypertrophy. The present studies were carried out to determine the properties of coronary K<SUB>Ca</SUB> channels in normal and hypertrophied hearts. These channels were measured from rabbit coronary smooth muscle cells using a patch clamp technique. The main findings of the present study are as follows: (1) the unitary current amplitudes and the slope conductance of coronary K<SUB>Ca</SUB> channels were decreased without changes of the channel kinetics in isoproterenol-induced cardiac hypertrophy; (2) the sensitivity of coronary K<SUB>Ca</SUB> channels to the changes of intracellular concentration of Ca<SUP>2&#8290;</SUP> was reduced in isoproterenol-induced cardiac hypertrophy. From above results, we suggest for the first time that the alteration of K<SUB>Ca</SUB> channels are involved in impaired coronary reserve in isoproterenol-induced cardiac hypertrophy.