A comparative study of nicotinamide nucleotide coenzymes during growth of the sheep and rat

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Abstract
Specific enzymic reactions were used to determine the concentration of both oxidized and reduced nicotinamide nucleotide coenzymes in the livers of lambs, sheep and rats. Concentrations of coenzymes were expressed as amount/unit wt. of tissue and as amount/nucleus (i.e. amount/average cell); Total amounts of coenzymes were compared on the basis of the dry weight and of the number of nuclei of the liver. During the normal growth of the liver in both sheep and rats, the concentrations of the total nicotinamide nucleotide coenzymes increased and reached a maximum value as development ceased. In the adult liver of both rats and sheep, the concentration of total coenzymes/nucleus was of the same order (approx. 490 [mu]m-moles/108 nuclei), and about twice the concentration found in livers of the young animals. The concentration of NAD was higher in the adult- sheep liver than in the rat, and the concentration of NADPH2 was much higher in the rat liver. The co-enzyme ratio ([NAD] +NADH2])([NADP] +[NADPH2]) fell from about 2[center dot]4 in the young to about 1[center dot]3 in the mature rat, and increased from about 1[center dot]6 in the lamb to about 2[center dot]5 in the adult sheep. These findings were discussed with reference to the growth and intermediary metabolism of lambs, sheep and rats.