RESPONSE OF PROTEIN-SYNTHESIS TO ANOXIA AND RECOVERY IN ANOXIA-TOLERANT HEPATOCYTES

Hepatocytes from the western painted turtle (Chrysemys picta bellii) d isplay a profound metabolic suppression under anoxia. Fractional rates of protein synthesis fell by 92% during 12 h anoxia at 25-degrees-C a nd were indistinguishable from the rate obtained with cycloheximide. N ormoxic recovery saw protein synthesis increase to 160% of control val ues and return to normal after 2 h. The GTP-to-GDP ratio, implicated i n the control of translation, fell threefold during anoxia. Purine nuc leotide phosphate profiles suggest that this change occurs through inc reasing concentrations of ADP and GDP, with concentrations of ATP and GTP and total purines remaining constant. The normoxic cost for protei n synthesis was calculated at 47.6 +/- 6.8 mmol ATP/g protein. Normoxi c protein synthesis accounted for 36% of overall ATP turnover rates, c lose to the extent of O2 consumption inhibitable by cycloheximide (28% ). Under anoxia, the proportion of ATP turnover utilized by protein sy nthesis did not change significantly. ATP turnover rates for urea synt hesis reflected a similar pattern, falling 72% under anoxia. These res ults reflect the cell's ability to suppress protein synthesis under an oxia in a manner that is coordinated with the reduction in total metab olic rate.