THE RATE OF INDUCTION OF THE MITOCHONDRIAL α-GLYCEROL-PHOSPHATE DEHYDROGENASE BY THYROID HORMONE IN ADULT AND SENESCENT RATS

The specific activities of the mitochondrial a-glycerolphosphate dehydrogenase from livers of adult (12-13-months old) and senescent (27-29-months old) hypothyroidic rats were measured at different intervals following the induction of enzyme synthesis by triiodo-L-thyronine. There were no significant differences between the two age groups in the rates of induction, the maximal levels of the induced enzyme, or the decreases in activity following the attainment of peak activities. These findings suggest that the biochemical machinery for protein synthesis in this tissue in aged animals is in no way impaired, at least in this specific model system, and that the livers of senescent rats are fully capable of responding to direct adaptive stress.