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

Abstract

Glucose-evoked potentials measured at low incubation temperatures were found to be highly tem-perature dependent (phase 1), but less so at high incubation temperatures (phase 2) and acclimatization of an 8[degree]C fish to 25[degree]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 acclimati-zation of Na transport across the intestine. 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 rise the steady transmural potential of the intestine. No changes in intesti-nal electrical parameters could be detected when fish, acclimatized to 8[degree]C, were heated at 25[degree]C for 15 hr. but after 20 hr. at the higher tem-perature, acclimatization to the new temperature was complete. Intes-tines from fish acclimatized to 8[degree]C, but which had first spent 15 hr. at 25[degree]C and then 10 hr. at 8[degree]C, still behaved qualitatively like 8[degree]C intestines, but the magnitude of the glucose-evoked potentials was slightly reduced. It is suggested as a working hypothesis that acclima-tization of the sodium-glucose interaction to different environmental temperatures involves the synthesis of new carrier molecules, quali-tatively different from the old ones.