Tryptophan, copper and zinc in hair of healthy subjects. Correlation with differences in hair pigmentation.

Tryptophan, copper and zinc levels were determined in the hair of 300 healthy subjects divided by sex, age and hair colour. Sex influences tryptophan content in hair, the levels of this amino acid being higher in males than in females. Tryptophan is also higher in infancy (2-5 years) and in both males and females aging around 80 years and over. Hair colour also influences tryptophan levels, which increase from fair to black hair. Copper levels are similar in hair of both males and females, while those of zinc are higher in women. Age influences the distribution of these two metals in human hair. Copper contents in hair of males are higher at the age 20-40 years. In females, values decrease over the age of 60 years. Instead, zinc levels are higher between 20 and 60 years in males, and between 13 and 19 years in females. As regards hair colour, copper is slightly higher in black hair in males and in fair hair in females, and lower in white hair in both sexes. Zinc values appear to be higher in red and lower in white hair in males. In females they are higher in black hair.

Enzyme activities and metabolites along the kynurenine pathway in mice with Harding-Passey melanoma.

Tryptophan metabolism has been studied in mice with Harding-Passey melanoma and in controls, after a load of 1.0 g/kg b.w. of L-tryptophan by determining ten urinary metabolites of the kynurenine pathway and some enzyme activities involved in the degradation of this aminoacid. Kynurenine was the only tryptophan derivative excreted in significantly higher quantities in mice with melanoma with respect to the controls. This result is in agreement with a significantly higher activity of hepatic tryptophan pyrrolase in mice with melanoma. Liver kynureninase and liver and kidney kynurenine aminotransferase activities were similar in the two groups of mice. These findings point to a possible role of tryptophan in the biogenesis of melanins in pathological conditions such as in melanoma.

Alterations of the tryptophan--nicotinic acid metabolism in vitiligo.

Tryptophan metabolism "via kynurenine" is altered in vitiligo: after a load of the amino acid the urinary excretion of 3-hydroxykynurenine and 3-hydroxyanthranilic acid is decreased, whereas that of xanthurenic acid and its 8-methyl ether is increased. The excretory values of the metabolites suggest a deficiency of the activity of kynurenine hydroxylase and kynunerinase, the enzymes involved in the metabolism of 3-hydroxykynurenine and 3-hydroxyanthranilic acid. The reduced excretion of 3-hydroxykynurenine, a tryptophan metabolite involved in melanin biosynthesis, may indicate a smaller utilization of tryptophan in the biogenesis of the melanins.