PLASMA CYSTEINE AND SULFATE LEVELS IN PATIENTS WITH CIRRHOSIS OF THE LIVER

1. Fasting levels of plasma cysteine, plasma sulphate and the plasma c ysteine/sulphate ratio were measured in patients with primary biliary cirrhosis and compared with those in patients with other liver disease , general intensive therapy unit patients and healthy subjects. 2. Pla sma cysteine was significantly elevated in patients with primary bilia ry cirrhosis (median 0.364 nmol/mg of protein, P < 0.0001) and patient s with other liver disease (median 0.445 nmol/mg of protein, P < 0.000 1), compared with healthy control subjects (median 0.125 nmol/mg of pr otein) and increased progressively with the severity of liver disease. Plasma cysteine was also elevated in intensive therapy unit patients (median 1.564 nmol/mg of protein) compared with healthy control subjec ts (P < 0.0001) and patients with other liver disease (P < 0.0001). 3. Plasma sulphate was reduced significantly only in patients with prima ry biliary cirrhosis (median 0.822 nmol/mg of protein) compared with h ealthy control subjects (median 1.37 nmol/mg of protein, P < 0.05). Th ere was no significant difference in plasma sulphate between disease g roups. 4. The plasma cysteine/sulphate ratio was significantly elevate d in patients with primary biliary cirrhosis (median 0.448, P < 0.0001 ) and patients with other liver diseases (median 0.394, P < 0.0001) co mpared with healthy control subjects (median 0.095). The ratio was als o elevated in intensive therapy unit patients (median 1.650, P < 0.000 1) compared with healthy control subjects and liver disease groups (P < 0.0001). 5. In conclusion, plasma cysteine rises in primary biliary cirrhosis and other forms of liver disease. This effect is not specifi c to liver disease, since cysteine is elevated in an heterogeneous gro up receiving intensive care. Impairment of trans-methylation and trans -sulphuration pathways does not explain the finding of increased plasm a cysteine. Since cysteine is elevated in non-hepatic disease, it may reflect the effect of muscle breakdown and the catabolic state. Impair ed activity of cysteine dioxygenase and impaired mitochondrial functio n may be contributory, but this