QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Patterson, J. I. Articles by Harper, A. E. Search for Related Content PubMed PubMed Citation Articles by Patterson, J. I. Articles by Harper, A. E.

Effect of Nicotinamide Intake on Urinary Excretion of N¹-Methylnicotinamide and Oxidation of [7a-¹⁴C]Tryptophan in the Rat¹

Departments of Nutritional Sciences and Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53706

Oxidation of tryptophan and urinary excretion of N¹-methylnicotinamide were studied in weanling rats fed ad libitum for 10 days 12% casein diets containing from 0 to 500 mg of nicotinamide per kilogram of diet. N¹-methylnicotinamide was measured in urine collected during the last 3 days of the experiment. After the feeding period, rats fed the niacin-free and 500 mg nicotinamide diets were placed in metabolic cages, and each rat was given 4 g (dry weight) of diet containing a tracer dose of DL-[7a-¹⁴C]tryptophan. Expired CO₂ was collected hourly for 10 hours. From rats consuming levels of nicotinamide ranging between 20 and 150 mg/kg of diet, N¹-methylnicotinamide excretion increased linearly with increasing nicotinamide intake. From these results and others from this laboratory (4), it was calculated that an additional 10–11 mg of dietary tryptophan above the approximately 20 mg/day essential for growth are needed by the growing rat for the formation of 1 mg of nicotinamide. The addition of 500 mg of nicotinamide per kilogram of diet to a niacin-free diet had no effect on the oxidation of DL-[7a-¹⁴C] tryptophan.

KEY WORDS: • amino acid oxidation • tryptophan • niacin formation • niacin formation from tryptophan

¹ Supported in part by the College of Agricultural and Life Sciences of the University of Wisconsin-Madison and by grant AM 10748 from the U. S. Public Health Service, Bethesda, Maryland.

² Present address: Department of Home Economics, Cook College, Rutgers University, New Brunswick, NJ 08903.

Manuscript received 24 September 1981.