Stimulation of sodium transport across the teleost urinary bladder by urotensin II

Active transport of sodium (measured as short-circuit current) from the lumen to the serosal side of the seawater-acclimated Gillichthys mirabilis urinary bladder (columnar cell region) is stimulated in vitro by urotensin II. The response is dose related over a calculated physiologically meaningful range of concentrations. There is a concomitant reduction in transepithelial resistance. Arginine vasotocin, another urophysial peptide, is without effect on short-circuit current and does not reduce resistance. India ink injection via the caudal vein demonstrates a direct vascular path from the urophysis to the urinary bladder, supporting the notion of the urinary bladder as a target for urotensin II. The effect of urotensin II on ion transport across the teleost urinary bladder is consistent with a possible role in seawater osmoregulation.