No abstract

Histamine has been isolated from virtually all mammalian tissues(l,2) and has been reported to exist in particularly high concentrations in the gastrointestinal tract of the dog and man (3,4,5). The intriguing p gsibility that endogenous histamine may be the final colmmon mediator of gastric acid secretion prompted us to investigate the relationship between histamine concentration and the mast cell content of the fundic, corporal and antral mucost of the canine Methods and materials. Under sodium pentobarbital anesthesia (2.6 mgJkg) the complete stomachs from 4 adult mongrel dogs were rapidly excised through a midline abdominal incision. The animals were then sacrificed. Each stomach was opened along the greater curvature and twelve 3 x 3 cm specimens of full thickness gastric wall were obtained from the areas indicated in Fig. 1. Each sample was divided into 2 equal parts for independent histologic examination and histamine assay. Specimens for histological examination were fixed for 12 hours in 4% aqueous lead subacetate and then for an additional 12 hours in 10% formalin. The tissue was then dehydrated in the usual manner and imbedded in paraffin. Sections were cut to 10 p thickness, stained with 1 % toluidine blue and mounted in "Permount".t The advantage of this mounting technique is that the specimens retain their staining characteristics for several months. Quantitation of mast cell populations was carried out by a modification of the technique originally described by Ritchie(6). A square grid measuring .223 mm on a side and divided into 49 squares ordered in 7 rows was placed in the eyepiece of the light microscope. Under 430 magnifica-s toimach. * Supported by a USPHS Glrmt, John A. Hautfiord Foundation and Dlonald J. Clowling Fund for Surgical Research. t Fisher Scientific Co., Fair Lawn, N. J.tions, a "swath" of mucosa, 0.223 mm in width, was quantitated for mast cells in 6 areas on each slide. Care was taken to utilize only those areas which were cut perpendicular to the mucosal surface as evidenced by the fact that the lumina of the glands were apparent throughout their entire course. In addition, the mast cell profile of the mucosa was determined by quantitating the number of cells which fell under each row of squares when the specimen was examined with the grid. The random counting error of this technique was determined by blindly recounting 20 slides after 4-6 weeks and was found to be 11.3%.The glandular mucosa from the specimen for histamine assay was carefully dissected free from the submucosal and muscular layers and was homogenized in 9 volumes of 0.4 N perchlolric acid. The amount of endogenous histamine present in the specimens was then assayed by the fluorometric method of Shore, Burkhalter, and Cohn (7). Results are reported as micrograms per gram of wet tissue. In this laboratory, the standard deviatioa of the technique, determined by assaying a large number of replicate samples, is t3.019 pg.