Immunocytochemistry of Kv1.5 potassium channel protein in cultured neonatal rat ventricular myocytes.

Of the six voltage-gated potassium channel subunits detected in adult rat heart, Kv1.5 channel is abundant and its expression is depressed in hypertrophied and infarcted myocardium. The effect of nonmyocyte cells (NMCs) on cardiac Kv1.5 channel expression was studied in cultured neonatal rat ventricular cells, using immunofluorescent cytochemistry with a polyclonal antibody against rat Kv1.5 channel protein. Co-culture with NMCs induced myocyte hypertrophy, but a downregulation of Kv1.5 channel expression. Similar changes were observed when pure myocyte culture was treated with medium supernatant of pure NMC culture. These findings suggested that some soluble factors produced by cardiac NMCs play important roles in the regulation of potassium channel density during myocardial hypertrophy.