Red cell carbonic anhydrase activity and chloride content in goldfish ( Carassius auratus L.) exposed to constant and diurnally-cycling temperatures

Abstract

1. 1. Plasma and red cell chloride concentrations increased at higher temperatures in goldfish acclimated to 20, 25 and 30°C. 2. 2. Red cell chloride in fish exposed to a sinewave, diurnal temperature cycle (25 ± 5°C) was similar to that of 20°C fish. Plasma levels were substantially lower. 3. 3. Cytosol carbonic anhydrase activity increased with temperature, and was more thermosensitive in 30° C-acclimated animals than in those at 20 and 25 ± 5°C. 4. 4. Cytosol non-hemoglobin protein levels were significantly reduced in the 30°C groups. 5. 5. It is postulated that differential thermosensitivity and activity variations with temperature may stem, in part at least, from acclimatory modifications in isozyme abundancies.