Effect of valinomycin on isolated urinary bladder of Pseudemys scripta. I. Effect on electrical parameters under aerobic conditions

Abstract

1. 1. Isolated hemibladders of the fresh-water turtle, Pseudemys scripta, were bathed on both surfaces by oxygenated, Na +-Ringer solution (17 mM HCO 3 − buffer) and were maintained in a short-circulated state. 2. 2. The cyclic dodecadepsipeptide antibiotic, valinomycin, was added to a final concentration of 1 μM to either the mucosal or serosal surface of one hemibladder while the paired hemibladder served as a time control. 3. 3. Addition of valinomycin to the mucosa resulted in a 60 ± 15% increase in total transbladder resistance ( R t ), in a 60 ± 10% decrease in short-circuiting current ( I sc ) and in a 40 ± 10% decrease in spontaneous open-circuited transbladder potential difference (PD oc) for the valinomycin-treated hemibladders relative to the control hemibladders. 4. 4. Half-maximal effect of valinomycin added to the mucosa was achieved 18 min after addition for I sc ; 24 min for PD oc; and 30 min for R t . 5. 5. Addition of valinomycin to the serosa did not result in any change in electrical parameters.