Effects of clofibrate on water permeability and short-cicuit current of toad urinary bladder

The effects of the oral antidiuretic drug clofibrate on water permeability of the urinary bladder of the toad, Bufo marinus, were studied. Clofibrate did not alter control water flow along an osmotic gradient. Water flow increases due to vasopressin were reversibly inhibited by 1 to 10 mM clofibrate from the serosal side. Clofibrate in the serosal bathing medium inhibited water flow increases due to cyclic AMP but not due to theophylline. Serosal clofibrate concentrations less than 1 mM or clofibrate in the mucosal solution (1 mM) was ineffective in inhibiting the osmotic water permeability response to vasopressin. Clofibrate in the serosal bathing medium (1 mM) inhibited base-line short-circuit current but had no effect on vasopressin-stimulated short-circuit current.