In vitro metabolism of creatinine, methylamine and amino acids by intestinal contents of normal and uraemic subjects.

An original method which uses in vitro anaerobic incubation at 37 degrees C followed by centrifugation, ultrafiltration, and ion exchange chromatography is described; it shows that faecal material suspended in physiological saline can destroy added creatinine. The rate of breakdown by suspensions from uraemic subjects (mean 780 mumol h-1kg-1 SEM 70) was slightly faster than in normal subjects (mean 550 mumol h-1kg-1 SEM 80). Methylamine concentration increased over eight hours as creatinine was metabolised and sarcosine appeared as an intermediate. The rates of these reactions varied within and between individuals and were inhibited by oxygen and centrifugation but not by oxytetracycline. Concentrations of free amino acids did not change significantly despite the formation of ammonia. This approach should be useful in studying the metabolic inter-relationships between intestinal contents and the host organism in health and disease.