Long-term starvation in Xenopus laevis daudin—I. Effects on general metabolism

Abstract

1. 1. The influence of starvation for 12 months on different physiological parameters was studied in the South African clawed toad, Xenopus laevis Daudin. 2. 2. During starvation for 12 months the animals lost between 35 and 45% of the initial body weight depending on sex. 3. 3. The experimental analysis of the starvation period showed two distinct phases. In females the first phase lasting about 4–6 months was characterized by a reduced oxygen consumption of about 30% of the fed state, a reduced nitrogen-excretion rate and decreased plasma concentrations of urea and lactate. An elevation of lipid utilization can be concluded from an increase in total lipids in plasma. Plasma glucose did not change significantly for four months of starvation. 4. 4. A transition to the second phase of starvation was characterized by a new start of decreasing oxygen consumption. 5. 5. In the second phase of starvation there was a short and small increase in metabolic activity followed again by a decrease. The increase in the nitrogen-excretion rate and plasma urea together with the declining concentration of proteins in plasma indicated an intensified protein catabolism. The plasma glucose concentration decreased continuously during this phase. 6. 6. Aldosterone and corticosterone in plasma were first shown to be reduced after 2–4 months of starvation and remained unchanged for the duration of the experiment.