Time course and nature of temperature-induced changes in sodium-glucose interactions of the goldfish intestine.

1. Glucose-evoked potentials measured at low incubation temperatures were found to be highly temperature dependent (phase 1), but less so at high incubation temperatures (phase 2) and acclimatization of an 8 degrees C fish to 25 degrees C resulted in the extension of phase 1 up to the environmental temperature of the fish. This change was only part of the mechanism controlling the acclimatization of sodium transport across the intestine.2. The temperature at which the glucose-evoked potential changed from phase 1 to phase 2 was approximately equal to the temperature at which glucose began to raise the steady transmural potential of the intestine.3. No changes in intestinal electrical parameters could be detected when fish, acclimatized to 8 degrees C, were heated at 25 degrees C for 15 hr, but after 20 hr at the higher temperature, acclimatization to the new temperature was complete.4. Intestines from fish acclimatized to 8 degrees C, but which had first spent 15 hr at 25 degrees C and then 10 hr at 8 degrees C, still behaved qualitatively like 8 degrees C - intestines but the magnitude of the glucose-evoked potentials was slightly reduced.5. It is suggested as a working hypothesis that acclimatization of the sodium-glucose interaction to different environmental temperatures involves the synthesis of new carrier molecules, qualitatively different from the old ones.