Free amino acids in biopsy specimens from the human colonic mucosa

The content of free amino acids and total protein was determined in endoscopic biopsy specimens from the rectum, descending colon, transverse colon, and ascending colon in 10 patients. The amino acids were quantified by ion-exchange chromatography and were detected by fluorescence. The amino acid pattern and the rank order of the individual amino acids in the colon were different compared to those in plasma. Glutamate, taurine, aspartate, glutamine, glycine, alanine, serine, lysine, valine, and ornithine were the 10 most abundant amino acids in the colon. The rank order was the same in all of the different segments of the colon. The concentrations of the amino acids decreased the more aborally the biopsies were taken. The protein content in the rectum was significantly lower than that in the transverse colon, but there were no difference between the different segments otherwise. The study demonstrated the possibility of determining free amino acids from endoscopic biopsies of human colonic mucosa. Biopsy specimens from the descending colon and/or rectum/sigmoid colon may be considered representative of the entire large intestine. The technique may be used for repeated sampling in studies of the amino acid metabolism of the intestinal mucosa.