Characterization of non-TCA-precipitable 'Lowry protein' in plasma of patients with acute renal failure.

An increase of 'Lowry protein' was observed in plasma supernatants obtained after TCA precipitation (final concentration 30.6 mmol/l) from patients with catabolic states. Therefore, a study was performed to evaluate whether this increase of 'Lowry protein' in plasma supernatants from post-traumatic ARF patients is caused by amino acids, peptides and low molecular weight proteins. Mixing different TCA concentrations with different proportions of plasma PTC-amino acids represent 16.0 +/- 4.9% to 42.2 +/- 5.9%) of 'Lowry protein' in ARF patients, whereas in controls a percentage between 35.4 +/- 4.6% and 74.6 +/- 10.6% was found. Therefore, we tried to find factors responsible for this difference. Urea, creatinine, uric acid, guanidines or dopamine are not responsible for this effect. Performing fast protein liquid chromatography and PTC-amino acid analyses of the peaks we could confirm that increased 'Lowry protein' observed in ARF patients is caused only in a small part by protein degradation products. Plasma free amino acid concentration showed no difference between ARF patients (2,054 +/- 162 mumol/l) and controls (2,503 +/- 105 mumol/l). Our data demonstrate that determination of 'Lowry protein' may be helpful in evaluation of catabolic state. However, this increase results mainly from non-protein related and until now not identified factors.