Phytate is the major storage form ofphosphorus in seeds and so is a common dietary constituent. Excessive ingestion of undegraded phytates can cause mineral deficiencies in humans. In addition, phytic acid is antineoplastic in animal models of both colon and breast carcinoma. There have been no previous studies quantifying phytase activity in the human small intestine although it is present in animals. Small intestinal phytase and alkaline phosphatase activity and distribution was measured in vitro in mucosal homogenates from two human small intestinal specimens obtained from transplant donors. Rat intestine was also studied for comparison. Phytase activity was found in human small intestine at low values (30 times less than that in rat tissue and 1000-fold lower than alkaline phosphatase in the same tissue). The activity was greatest in the duodenum and lowest in the ileum. In conclusion, the normal human small intestine has very limited ability to digest undegraded phytates. Although this may have adverse nutritional consequences with respect to metabolic cation imbalances, the presence of undigested phytate in the colon may protect against the development of colonic carcinoma.

SUMMARY The effects of porcine vasoactive intestinal peptide (VIP) and bovine pancreatic polypeptide (PP) on jejunal, ileal, and colonic fluid transport were studied in the rabbit. VIP produced secretion in the small intestine (jejunum > ileum) but did not affect absorption in the colon. PP Poole, England). A mixture of 95% oxygen and 5% carbon dioxide was bubbled through the perfusion fluid continuously. Alterations in fluid transport were determined from changes in the concentration of the non-absorbable marker PEG 4000 assayed by a turbidimetric method.'4 A Schuco pump (multi-mini model) was used to drive the perfusion solution through the intestinal loops at a rate of 15 ml/min. A polyethylene catheter (external diameter 3 mm-McCarthy's Surgical Limited, London, England) was inserted (via a cut-down on the right femoral artery) with its tip high up in the abdominal aorta. Throughout the experiments, pooled rabbit plasma, diluted 1 in 4 in isotonic saline, to which 5% (v/v) of the protease inhibitor aprotinin (Trasylol 20000 K IU/ml, Bayer, Germany) was added, was infused intra-aortically. This infusate also served as a vehicle for infusing porcine VIP (kindly donated by Professor V Mutt) at a rate of 0-1 ,ug/kg/min (30 pmol/kg/min) or boyine pancreatic polypeptide (kindly donated by Dr R E Chance) at a rate of 0-2 ,ug/kg/min (50 pmol/ on 9 May 2018 by guest. Protected by copyright.

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