Zinc deficiency and alterations of free amino acid levels in plasma, urine and skin extract

Abstract

The effects of zinc deficiency, in rats, on the levels of free amino acid in urine, plasma and skin extract were studied. In urine, significantly higher concentrations of taurine, urea, threonine, glutamic acid, valine, isoleucine, leucine and lysine were observed in zinc-deficient rats. In plasma, however, the levels of most individual amino acids in zinc-deficient rats were about the same as those in zinc-supplemented pair-fed controls with the exception of threonine, leucine and isoleucine. These three were significantly higher in rats receiving zinc-deficient diet. On the other hand, the zinc-supplemented ad libitum-fed rats had a significantly increased concentration of taurine, aspartic acid, threonine, serine, glutamic acid, alanine, lysine and arginine than either the pair-fed zinc-supplemented rats or zinc-deficient rats. In skin extracts, threonine, valine, leucine tyrosine, lysine, methionine, cystine, aspartic acid and alanine levels were significantly lower in zinc-deficient rats as compared to zinc-supplemented ad libitum-fed controls. However, the zinc-deficient rats had the same amount of methionine, cystine and glycine as the zinc-supplemented pair-fed rats. This observation suggests that the impairment of skin protein synthesis from injected labeled amino acids in zinc-deficient rats as opposed to zinc-supplemented pair-fed controls is not related to the availability or pool size of the precursors.