Effects of riboflavin deficiency on metabolism of nitrosamines by rat liver microsomes
Wang, T.; Miller, K.W.; Tu, Y.Y.; Yang, C.S.
Journal of the National Cancer Institute 74(6): 1291-1297
1985
ISSN/ISBN: 0027-8874 PMID: 3923247 Document Number: 262573
The effects of riboflavin deficiency on the metabolism of N-nitrosodimethylamine (DMN) and other nitrosamines were examined in rats. After weanling rats were given a riboflavin-deficient diet, the development of the deficiency was monitored by the growth rate and the erythrocyte glutathione reductase activation coefficient. In the riboflavin-depleted rats, the liver microsomal NADPH-cytochrome c reductase activity was lower but the cytochrome P450 content was higher than that of the control. The metabolism of DMN was dependent on the severity of the deficiency. During mild deficiency, which was observed mainly with Sprague-Dawley rats, the microsomal DMN demethylase (DMNd) activity was increased 30 to 80%, but the metabolism of N-nitrosomethylbenzylamine and 3 other nitrosamines was slightly decreased. Dietary restriction in the pair-fed group also caused an increase of DMNd activity above that of the freely fed control group due to a partial fasting effect. During severe deficiency, which was observed mainly with Wistar rats, the metabolism of DMN and the oxidation of benzopyrene were decreased. Preincubation with FAD and FMN increased the DMNd activity of the microsomes from riboflavin-depleted rats but not that from control rats.