Modulation of Na/K-ATPase activity by isoproterenol and propranolol in human non-pigmented ciliary epithelial cells

Purpose: The present study investigates whether beta -adrenoreceptor agents such as isoproterenol and propranolol can regulate Na+-K+-ATPase activity in cultured human non-pigmented ciliary epithelial cells. Methods: Human non-pigmented ciliary epithelial cells (ODM2) were grown to confluence. The active ion transport mediated by the Na+-K+-ATPase was eval uated by measuring ouabain-sensitive rubidium (Rb+) uptake. In a first set of experiments, cells were exposed to the beta -adrenoreceptor agonist isop roterenol (0.01-10 muM). In a second set of experiments, cells were exposed to isoproterenol (1 muM) in the presence of different concentrations of th e beta -adrenoreceptor antagonist propranolol (0.01, 0.1, 1 muM). Results: In a concentration-dependent manner, isoproterenol induced an incr ease in Na+-K+-ATPase activity. The maximal Na+-K+-ATPase activity was obse rved at a concentration of 1 muM of isoproterenol (283 +/- 58%, P < 0.001). The increase in Na+-K+-ATPase activity evoked by isoproterenol (1 <mu>M) w as inhibited, in a concentration dependent manner, by propranolol (maximum: 659 +/- 39 vs. 141 +/- 42 pM/mg protein/min, P < 0.01). Conclusion: The <beta>-adrenoreceptor agents isoproterenol and propranolol are apparently able to modulate Na+-K+-ATPase activity in cultured human no n-pigmented ciliary epithelial cells.