BODY FLUIDS AND EFFECT OF HEREDITARY DISORDERS 209 
transport mechanisms affecting tubular reabsorption and that tryptophane is in- 
volved secondarily. 
Cystinurta. It has been known for 150 years that certain people form cystine stones 
in the urinary tract and that the disorder was familial. Further investigations, carried 
out since the advent of chromatography, have shown that not only cystine is ex- 
creted in larger amounts than usual but there is also an increased excretion of lysine 
TYR 

SER 
GLUT 


LYS 
ETH-POg 
Fig. to. A paper chromatogram of the urine of a child with galactosaemia. 
arginine, and ornithine*®: *’, But for the fact that cystine has a low solubility in water 
and urine and consequently tends to form calculi when excreted in a supersaturated 
concentration these patients would remain healthy as the daily loss of these amino 
acids is easily compensated for in the dietary intake. The urine chromatogram of a 
typical cystinuric patient is shown in Fig. g. The cystine is oxidized before chromatog- 
raphy as the resulting cysteic acid behaves more reliably than the parent substance 
which tends to streak. The plasma amino acid levels are normal in these subjects but 
the cystine level tends to be slightly low®*. The metabolic error in this disease is ap- 
parently an inability, partial or complete, to reabsorb cystine from the glomerular 
References p. 217/219 
