Sodium Flux Through the Gills of Goldfish

Abstract

The gills of the goldfish (Carassius auratus) can transport Na ions from a 0.001 [image]. external soln. to an internal environment which is approx. 0.1 [image]. with respect to the Na ion. Under conditions of stress, however, the fish may also lose Na to its external environment, apparently through the gills. The nature of this changing permeability was explored by measuring the Na movements through the gills by means of Na22. in these expts. urinary Na was collected separately and it is assumed that alterations of the ion content of the water are due primarily to activity of the gills. The fish were placed in 0.001 [image] NaCl containing Na22 and both net Na concn. and Na22 were followed for 12 hrs. Total concn. of Na increased an avg. of 20% at the end of 1 hr. and then decreased for the next 11 hrs., as active uptake became evident. Na22 Was found to decrease at a steady rate over the entire 12 hr.-period, indicating that active uptake continued during the time that there was a gross of loss of Na from the fish. The rate of Na uptake for a 30 g. fish, as measured by the Na22, was 0.43 mg./hr. A 2d series in which Na22 Was injd. into the fish by intracardiac puncture demonstrated a moderate loss of Na22 from the gills throughout the 12 hrs., but the rate of loss was greatest during the first hr. Na absorption by the fish gill proceeds at a steady rate which normally more than replaces the loss through the gills, but under the stress produced by handling the fish, there is an increase in gill permeability and Na loss exceeds the capacity of the uptake mechanism.