Tissue and Whole Blood Concentrations of Nicotinamide Nucleotides

1 Tissue and Whole Blood Concentrations of Nicotinamide Nucleotides 

Measurement of liver and other tissue concentrations of NAD(P) gives a precise estimate of niacin nutritional status and seems to be the most sensitive indicator in experimental animals. Measurement of the whole blood concentration of NAD (P) may serve the same purpose there is agood correlation between blood and liver concentrations of nicotinamide nucleotides in experimental animals. The sensitivity of the method is such that reproducible determinations can be carried out on finger-prick samples of 200 jxL of blood (Bender etal., 1982). 

Erythrocyte NAD falls during niacin depletion and rises during repletion in human subjects. Erythrocyte NADP is unaffected, and the ratio of NAD NADP provides a useful index of niacin nutritional status, with a ratio 1.0 indicating deficiency (Eu et al., 1989). 

2 Urinary Excretion of/V -Methyl Nicotinamide and Methyl Pyridone Carboxamide 

The most widely used method for assessing niacin nutritional status is measurement of the urinary excretion of niacin metabolites. Table 8.1 shows the excretion of -methyl nicotinamide and methyl pyridone carboxamide in niacin adequacy and deficiency. 

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