Unidirectional fluxes of na+, cl−1 and water in fingerling channel catfish, ictalurus punctatus

Abstract

Abstract 1. 1. The influx of Na+ and Cl−(as 22Na+ and 36Cl−1) was measured in fingerling channel catfish (Ictalurus punctatus) and was found to be equivalent in a 7–8 g fish to about 20 and 40%, respectively, each day of their total body Na or Cl. In the smallest fish (l g), the rate of flux was 3–4 times as great as in larger (15g) ones. 2. 2. Unidirectional flux of water (as efflux of 3H-water) was very rapid, equivalent to about 3 times the total body water each hour. 3. 3. Drinking was relatively small equivalent to about 2.5% of the body weight each day (6% at pH 5) and so contributed little to the above fluxes, which presumably mainly occurred across the gills and possibly the skin. 4. 4. Influx of Na+ was reduced when the Ca2+ concentration was increased from 0.1 to 3 mM. Changes of pH between 8.3 and 5 and the presence of 0.01 mM A13+ such as may result from “acid rain” did not change Na influx. 5. 5. Efflux of Na+ was increased when the pH was decreased from 7.3 to 5, but neither Ca2+ (3 mM) nor Al3+ (0.01 mM at a pH of 5) had a significant effect. 6. 6. The unidirectional flux of water was reduced by 0.01 mM Al3+ at pH 5, but it was unchanged by a pH of 5 alone or 3 mM Ca2+.