PROTEIN-SYNTHESIS IN THE LIVER OF BUFO-MARINUS - COST AND CONTRIBUTION TO OXYGEN-CONSUMPTION

While many estimates of the contribution of protein synthesis to metab olic rate exist for a variety of animals, most rely on theoretical cos ts of protein synthesis. The limitations of this approach are that the oretical costs depend upon variable estimates of ATP cost per peptide bond. In addition, they do not take into account the fact that there a re protein-specific pre- and post-translational costs. By inhibiting, protein synthesis with cycloheximide and measuring the resultant decre ase in oxygen consumption, we have measured the actual cost of protein synthesis and its contribution to metabolic rate in an in vitro syste m of tissue slices from Bufo marinus. Such measurements exist for endo therms, but there are few such measurements for ectotherms, and none h ave been done previously for amphibians. The cost of protein synthesis in liver slices from B. marinus was 7.32 +/- 1.19 nmol O-2 . g((prote in))(-1)((x) over bar +/- SE, n = 48) and protein synthesis accounted for 12% of the total metabolic rate of this tissue. This cost is compa rable to values measured for other ectotherms although the contributio n of protein synthesis to metabolic rate is at the lower end of the ra nge of estimates for other ectotherms. (C) 1998 Published by Elsevier Science Inc.