| Abstract: | ![]()
The urinary bladder of Amphiuma exhibits stable transport properties and an electrical potential difference in vitro. The lumen is significantly negative to the serosa and under short-circuited conditions flux rations for Na and Cl of 5.92 +/- 0.42 and 1.81 +/- 0.20, respectively, were observed. The close agreement between the short-circuit current and net Na flux suggests that most, if not all, of the current is carried by Na. Both ouabain and amiloride decreased the short-circuit current and the mucosal-to-serosal (M leads to S) flux of Na. Furosemide caused a transient increase in the M leads to S flux of Na and Cl but ADH was without effect. In bladders that had high transmural resistance, a net movement of K in the M leads to S direction under short-circuited conditions with flux ratios of up to 2 could be observed. The epithelium of the Amphiuma bladder consists of three cell types: granular cells, basal cells, and mitochondria-rich cells. No goblet cells are present. The mitochondria-rich cells comprise less than 5% of the population of the surface epithelium in Amphiuma in contrast to other amphibian bladders, where it accounts for up to 25% of the population. |
