Sodium exchange process in lower vertebrates studies by means of 24Na. Their interpretation as a 'purification' of radioactive water

Fresh-water fish and amphibians live in an aquatic medium which is very hypotonic with respect to their internal medium. By osmosis the water passes through their permeable teguments (gills, mucous membranes, skin). It is known from the work of Krogh (1937-1939) that this water is eliminated by the kidney, which emits a copious diluted urine. Yet however great the dilution, the urinary excretion results in a loss of salts for the organism. This loss is compensated, even in the absence of any nourishment, by active absorption of ions. Some recent workers have attempted, by using radioactive isotopes, to establish the balance between the input and output flows of ions through the permeable membranes in vivo, whereas chemical analytical methods only allow the net result of these exchanges to be obtained. We have attempted to present here a new method for the simultaneous measurement of the sodium flow takes over the whole animal. This method has been applied to the fresh-water fish Carassius auratus and to the frog Rana esculenta. In the course of this investigation we have considered interpreting it as a 'purification of radioactive water'. (author)