Effect of propranolol and nifedipine on in vitro fluid absorption by the isolated perfused proximal convoluted tubule of the rabbit

ABSTRACT

The inhibition of fluid absorption (Jv) by the antiarrhythmic and antihypertensive drugs propranolol and nifedipine, which increase cytosolic Ca*+ concentration, was studied using the isolated rabbid proximal convoluted tubule perfused in vitro. Proximal convuluted tubules were perfused and bathed with a modified Krebs-Henseleit solution containing bovine serum albumin. Jv was measured after a 30-min control period, after 40 min with eithe 0.1 mM propranolol or 1.0 mM mifedipine on the peritubular side and after a 40-min recovery period. Both drugs inhibited Jv (58% propranolol, and 21% nifedipine) The 40-min recovery period was sufficient to reserve the effect of nifedipine, but propranolol-treated tubules (N=6) only reached 78% of the control Jv value. These results demonstrate that antiarrhythmic and anthypertensive drugs are powerful inhbitors of net fluid absorption by exerting a direct effect on proximal or distal tubule cells, thus acting like "local diuretics"