Temperature-induced changes in sodium transport and Na +/K +-adenosine triphosphatase activity in the intestine of goldfish ( Carassius auratus L.)

Abstract

1. 1. The transfer of sodium and fluid across everted sacs of goldfish intestine fell to half the control values 18–24 hr after raising the environmental temperature from 16 to 30°C. The Na +/K +-ATPase activity fell in membranes prepared from 16°C adapted fish kept at 30°C but this took 20 days to become apparent. 2. 2. The amount of tritiated ouabain bound to membranes prepared from the intestines of 16°C adapted fish was the same as that bound to membranes prepared from 16°C adapted fish kept at 30°C for 20 days. The time course of ouabain binding was also the same, both in the presence and absence of ATP. The ATP-dependent binding was 4 times the non-specific binding. 3. 3. The turnover number for the Na +/K +-ATPase system (ATPase activity/ amount of ATP-dependent bound ouabain) fell by one third when 16°C adapted fish were kept at 30°C for 20 days. The turnover numbers for Na +/K +-ATPase from fish kept at 30°C for shorter periods of time were not significantly differrent those obtained from the 16°C adapted fish. 4. 4. The discrepancy between the time taken for sodium transport and Na +/ K +-ATPase activity to adapt suggests that the two are not directly related.