Effect of partial outlet obstruction of the rat urinary bladder on the response to alterations in the concentrations of potassium and calcium.

1. The contractile response of the 7 day obstructed bladder to field stimulation was significantly increased from that of the control bladder. 2. In the presence of 1.8 mM calcium (normal Tyrode's solution) the contractile response of control bladders to low-frequency field stimulation was significantly enhanced by increasing the potassium concentration from 2.5 to 7.5 or 12.5 mM. 3. Increasing the potassium concentration had no effect on the response of the obstructed bladder to low-frequency field stimulation. 4. Increasing the extracellular calcium concentration enhanced detrusor contractility in a dose-dependent manner in both control and obstructed bladders. 5. The magnitude of the effect of increasing the extracellular calcium concentration were greater in the obstructed bladder than in the control bladder. 6. These results suggest that calcium transporting mechanisms of the cell membrane and intracellular calcium storage and mobilization may be significantly affected by partial outflow obstruction.