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Tyrosine supplementation in chronic experimental uremia
Biochemical Medicine
|August 1, 1983
Summary
Supplementing tyrosine in uremic rats did not improve growth or correct amino acid imbalances. Impaired kidney function, not tyrosine deficiency, altered tyrosine and phenylalanine levels in uremia.
Area of Science:
- Nephrology
- Biochemistry
- Nutritional Science
Background:
- Uremic subjects exhibit low tyrosine levels, potentially due to impaired phenylalanine hydroxylation.
- This suggests tyrosine might be an essential amino acid in uremia, necessitating dietary supplementation.
Purpose of the Study:
- To investigate the effects of dietary tyrosine supplementation on growth and tyrosine/phenylalanine metabolism in uremic rats.
Main Methods:
- Uremic rats (7/8 nephrectomy) and controls (sham-operated) were fed standard or tyrosine-supplemented diets for 21 days.
- Growth parameters and liver phenylalanine hydroxylase activity were assessed.
- Plasma tyrosine and phenylalanine levels were measured.
Main Results:
- Tyrosine supplementation did not improve growth parameters (body weight gain, tibial length, muscle mass, tissue protein) in uremic rats.
- While tyrosine supplementation normalized plasma tyrosine:phenylalanine ratios, basal levels were low in uremic rats on standard diets.
- Decreased kidney phenylalanine hydroxylation in uremia, linked to renal mass loss, was identified as the primary factor affecting plasma amino acid levels.
Conclusions:
- The study does not support the hypothesis that tyrosine is an essential amino acid in uremia.
- Impaired renal function, rather than tyrosine deficiency, is the main driver of altered tyrosine and phenylalanine metabolism in uremia.