Maximal activities of enzymes of intermediary metabolism in the estivating terrestrial snail Cepaea nemoralis

Abstract

The effects of estivation on maximal activities of key enzymes of aerobic, carbohydrate, lipid, ketone body and amino acid metabolism were studied in tissues of the terrestrial snail Cepaea nemoralis. With the exception of a 40% decrease in citrate synthase activity in hepatopancreas, enzyme activities were unaltered in all tissues following 6 weeks of estivation. Activities of enzymes of lipid, ketone body and carbohydrate metabolism were reduced in the kidney, when expressed on a per g wet tissue weight basis. However, estivation resulted in a near-doubling of kidney weight, though protein concentration of this tissue was decreased by 27%. When enzyme activities were expressed as units per mg −1 protein, no changes were observed with estivation in kidney. It was suggested that the changes in kidney weight are due to the storage of metabolic by-products, perhaps uric acid. No change in weight or protein content of heart or hepatopancreas were observed. These results suggest that no universal down-regulation of enzyme activities occurs during long-term estivation.