Human intestinal mucosa contains acyl-CoA:cholesterol acyltransferase activity. The enzyme has been studied by using oleylcarnitine, CoA and carnitine palmitoyltransferase as an oleyl-CoA regenerating system. The enzyme was found in the particulate fraction of the cells, it had a pH optimum between 7.2 and 8.2, and was inhibited by taurocholate. The specific enzymic activity in biopsies from intestinal mucosa of normal men was found to be 3.6 +/- 1.37 nmol cholesteryl ester formed mg protein-1 h-1, an activity which can account for all cholesteryl esters in intestinal lymph. Low enzymic activity was found in biopsies from patients with small intestinal disorders. Two pancreatectomized patients had values within the normal range.
Neurotensin was added to human jejunal mucosal biopsy specimens from six individuals. Fifty-seven per cent degranulation of mast cells was seen at a concentration of neurotensin of 10(-9) M and 43% at 10(-6) M, as compared with 31% with IgE antibody/antigen. There was no change in degranulation with neurotensin when IgE was added to biopsy specimens before neurotensin in a 10(-6) M solution. This effect of neurotensin on human jejunal mast cells supports the evidence for receptors for neurotensin on mast cells shown in rat experiments.
Sera from 3 allergic patients with specific IgE antibodies as shown by RAST were used to sensitize jejunal mucosa obtained from surgical patients. The sensitized specimens were challenged with the appropriate antigens to the specific IgE shown in the sera, Non-challenged sensitized specimens were used as controls to determine mast cell degranulation. The mast cells were counted in a defined area in the mucosa immediately adjacent to the muscularis mucosa. Mast cell degranulation was 47 percent in a timothy pollen system, 40 percent in an eggwhite system, and 33 percent in a codfish system. The results of the investigation indicates that mast cells in the human jejunal mucosa are able to react in the same manner as mast cells in the human lung. The experimental model described appears suitable for studying the allergic reaction in the gastrointestinal tract and the effect of pharmacotherapy in this respect.
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