Determinants in the pathways followed by the carbons of acetone in their conversion to glucose.

[2-14C]Acetone was infused into rats that were fed or fasted. Each was infused with either a trace quantity of acetone or a large quantity that resulted in a blood concentration of acetone of at least 4 mM. The distribution of 14C in the carbons of glucose from each rat was determined. Two of the rats were given acetone in their drinking water and one was diabetic. Whether a rat was chronically exposed to acetone, fed or fasted, normal or diabetic, if given the trace dose, over 80% of the 14C in the glucose it formed was in carbons 1, 2, 5, and 6 of the glucose. If a rat was given the large dose, about 50% was in carbons 3 and 4. Thus, the major determinant of the pathways followed by acetone when it is metabolized is its concentration and not the prior dietary state of the animal or its previous exposure to acetone. Incorporation into carbons 1, 2, 5, and 6 occurs in the conversion of the carbons of [2-14C]lactate into glucose, whereas incorporation into carbons 3 and 4 occurs in the conversion of the carbons of [1-14C]acetate into glucose. Therefore, at high acetone concentration, the pathway that has been proposed for acetone's metabolism via acetate predominates, and via acetate there can be no net synthesis of glucose from acetone. When rats were given cyanamide and then the large dose of acetone, 74% of the 14C in the glucose they formed was in carbons 3 and 4 of the glucoses. Thus, the relative contribution of the pathway to lactate, or its metabolic equivalent, that has been proposed appears to be lessened by the administration of an aldehyde dehydrogenase inhibitor.