RELATIONSHIP BETWEEN STRUCTURE AND FUNCTION OF LIVER-MITOCHONDRIA FROM HIBERNATING AND ACTIVE GROUND-SQUIRRELS, CITELLUS-UNDULATUS

1. Electron microscopy of liver tissue preparations, obtained from hib ernating ground squirrels, reveals mitochondria in a condensed state. 2. When kept on ice, mitochondria isolated from the livers of hibernat ing and active ground squirrels are in a shrunken state. 3. Incubation of mitochondria isolated from the livers of active ground squirrels i n the presence of succinate, at 27-degrees-C, results in mitochondrial swelling, while mitochondria from hibernating ground squirrels under the same conditions remain relatively shrunken. 4. The swollen mitocho ndria from active ground squirrels show high oxidative activity, while the shrunken mitochondria from hibernating animals show low oxidative activity. 5. Swelling of mitochondria from hibernating ground squirre ls in a hypo-osmolar medium is accompanied by a significant increase i n oxidative activity. 6. It is inferred that the shrinkage of hibernat ing ground squirrel mitochondria is one of the main causes of the inhi bition of oxidative activity and other mitochondrial functions during hibernation.