The effect of a semisynthetic diet on the profile of urinary conjugates in male adults

Abstract

The effect of a semisynthetic diet on urinary conjugate levels was determined in 18 male adults (22 to 40 years). Subjects consumed a self-selected diet for 3 days and a semisynthetic diet for 7 days. Glucuronides and mercapturates were quantified spectrophotometrically using naphthoresorcinol and Ellman's reagents, respectively. Atomic absorption was used to measure barium chloride-precipitated sulfate for sulfoconjugates. Conjugated amino acids were determined by high performance liquid chromatography of phenylisothiocyanate derivatives. A multivariate analysis of variance was used to compare the means of the dietary periods, and a repeated measures analysis with Helmert transformation was used to determine response to dietary change. Mercapturates and amino acid conjugates were most sensitive to dietary change, with quantities excreted decreasing by about 50% during the semisynthetic diet period (0.29 versus 0.16 mmol/24 hr; 5.99 versus 3.06 mmol/24 hr, respectively). Glucuronides were the least responsive to dietary change, with no significant difference between the means of the two diet periods (self-selected diet, 2.98; semisynthetic, 3.05 mmol/24 hr). Sulfoconjugate levels exceeded those of the other conjugates measured. Sulfoconjugates were initially decreased on the semisynthetic diet (5.28 versus 3.98 mmol/24 hr), but by day 4, sulfo-conjugate excretion began to increase. In summary, the quantity of conjugates excreted were found to be sensitive to dietary changes, with some pathways more responsive than others.