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

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.

Human non-pigmented ciliary epithelial cells (ODM2) were grown to confluence. The active ion transport mediated by the Na(+)-K(+)-ATPase was evaluated by measuring ouabain-sensitive rubidium (Rb+) uptake. In a first set of experiments, cells were exposed to the beta-adrenoreceptor agonist isoproterenol (0.01-10 microM). In a second set of experiments, cells were exposed to isoproterenol (1 microM) in the presence of different concentrations of the beta-adrenoreceptor antagonist propranolol (0.01, 0.1, 1 microM).

In a concentration-dependent manner, isoproterenol induced an increase in Na(+)-K(+)-ATPase activity. The maximal Na(+)-K(+)-ATPase activity was observed at a concentration of 1 microM of isoproterenol (283 +/- 58%, P < 0.001). The increase in Na(+)-K(+)-ATPase activity evoked by isoproterenol (1 microM) was inhibited. In a concentration dependent manner, by propranolol (maximum: 659 +/- 39 vs. 141 +/- 42 pM/mg protein/min, P < 0.01).

The beta-adrenoreceptor agents isoproterenol and propranolol are apparently able to modulate Na(+)-K(+)-ATPase activity in cultured human non-pigmented ciliary epithelial cells.