The electrical properties and active ion transport across the urinary bladder of the urodele, Amphiuma means

Abstract

1. The electrical properties and the active transport processes of the isolated urinary bladder of the urodele, Amphiuma means, were studied by mounting this tissue as a flat sheet between two halves of a lucite chamber. The mean transepithelial potential difference was 70-2 +/- 2-3 mV (serosa positive), the mean short-circuit current was 10-9 +/- 0-5 micrionA/mg of dry weight and the mean transepithelial d.c. resistance was 6540 +/- 374 omega mg of dry weight. 2. The short-circuit current (Isc) accounted for 92% of the net 22Na+ flux from the mucosa to the serosa. The difference resulted from a transport of 36Cl- in the same direction as sodium. 3. The active sodium transport exhibited typical saturation kinetics, having a Km of 15-4 m-equiv/l. and approaching zero order at 60-70 m-equiv/l. The transepithelial potential difference increased linearly with the log of the mucosal sodium concentration at a rate of 50-3 mV per tenfold concentration change. 4. In the absence of the major anions (HCO3- and Cl-) from the bathing solutions, the electrical properties and the sodium influx decreased to less than 40% of their control values. The presence of only one of these two anions in the serosal bathing solution was sufficient to maintain these parameters. 5. Amiloride (10(-5)M) and ouabain (10(-6)M) inhibited the sodium transport 97% and 85% respectively. Amphotericin B (10(-6)M) stimulated the sodium transport 47%. Furosemide (10(-3)M) inhibited the chloride transport 43%. The sodium transport was insensitive to the action of two enurohypophyseal peptides tested, lysine-vasotocin and pitocin.