Nicotinamide coenzyme concentrations in livers of normal, starved and alloxan-diabetic rats

Abstract

The concentrations and ratios of nicotinamide coenzymes has been estimated by a fluorimetric method in liver samples from normal, starved and alloxan-diabetic rats. The assay had adequate precision to discriminate differences between animals in NAD, NADH2 and NADPH2, but not NADP. Compared with normal, NAD concentration was significantly lower and NADH2 higher during starvation, but not during diabetes. NADPH2 was lower during diabetes but higher during starvation. The ratio NAD/NADS2 was decreased during starvation but not diabetes, and NADP/NADPH2 was increased during diabetes but not starvation. The results suggest that the lipogenic defects during food deprivation and in alloxan-diabetes are different, at least with respect to the roles played by the nicotinamide dinucleotide coenzymes. If this is the case, the low NADPH2 concentrations found in diabetic-rat liver would be consistent with this lipogenic defect being partly due to a diminished availability of this co-enzyme. The high NADPH2 concentration found in starved-rat liver is consistent with its accumulation due to loss of enzymes which utilize it. Alternatively, if all the causes of the total lipogenic defect which develops during food deprivation and in diabetes are identical, they would not include changes in the concentrations of the nicotinamide adenine dinculeotides.