Gastrointestinal urease in man. I. Activity of mucosal urease.

Gastrointestinal urease in man. II. Urea hydrolysis and ammonia absorption in upper and lower gut lumen and the effect of neomycin.

“…The findings in this study and in an investigation in vitro carried out concurrently (Aoyagi et al, 1966), seen in perspective with other reports (Fossel, 1948;Kornberg et al, 1954;Kornberg and Davies, 1955;Walser and Bodenlos, 1959;Conway et al, 1959;Rappoport and Kern, 1963;Visek and Thomson, 1964), indicate that both mucosal and 637 bacterial urease are present in the gastrointestinal tract of man. The morphogenetic effects of the gut flora (Dubos and Schaedler, 1964), as well as the possibility of contamination and the difficulty of complete separation, impede identification of the mucosal or bacterial origin of enzymes in the bowel.…”

“…By contrast, urease-producing bacteria abound in the colon (Cregan and Hayward, 1953;Rosebury, 1962;Donaldson, 1964), where concentrations of the enzyme in mucosal homogenates from the human large intestine are relatively low (Fossel, 1948;Aoyagi et al, 1966). The urease activity measurable under the circumstances of the present study was bacterial in origin and was confined to the lower part of the gastrointestinal tract.…”

“…There was no evidence that the absorptive defect sometimes induced by the drug (Jacobson and Falcon, 1961) affected ammonia, since blood ammonium concentrations after ammonium acetate was given were not influenced by neomycin. The failure of urea administered by mouth to cause hyperammonaemia was surprising, since mucosal urease activity is much higher in the upper part of the gastrointestinal tract than in the ileum and large bowel (Fossel, 1948;Aoyagi et al, 1966). Moreover, increased concentrations of ammonia in blood and gastric juice have been reported when urea has been given by vein, the inference being that urea diffuses from blood to mucosal cells and is there hydrolyzed to ammonia, which enters the circulation or the stomach (Rappoport and Kern, 1963;Fleshler and Gabuzda, 1965).…”

“…The morphogenetic effects of the gut flora (Dubos and Schaedler, 1964), as well as the possibility of contamination and the difficulty of complete separation, impede identification of the mucosal or bacterial origin of enzymes in the bowel. However, the stomach and jejunum contain the highest mucosal concentrations of urease in the gastrointestinal tract (Fossel, 1948;Aoyagi et al, 1966), yet are normally sterile or harbour only a scanty bacterial flora (Cregan and Hayward, 1953).…”

The Role of the Colon in Urea Metabolism in Man

“…Studies of urease activity in man (Aoyagi, Engstrom, Evans & Summerskill, 1966; have shown that, apart from small quantities of mucosal urease in the stomach and small bowel, intestinal urease is bacterial in origin and is located in the colon.…”