THE MAST CELLS 



line with what we have found elsewhere. On the other hand, when conditions 

 in the overlying mucosa are examined, it is evident that here the rapid fall off 

 in the mast-cell content (average, five cells per field) is not accompanied by 

 a proportionate reduction in tissue histamine (average, 76 \xg. /g.) until a region 

 close to the surface of the mucosa is reached. There is, in fact, almost a fourfold 

 difference between the histamine-mast cell ratios in the submucosa and in the 

 deeper mucosa. As stated above, there is good reason for believing that the 

 histamine in the submucosa is due to its high content of mast cells; hence it is 

 clear that something other than mast cells must be binding the histamine in 

 the mucosa. 



The most obvious choice for this second component which binds histamine 

 in hog pyloric mucosa is the mucin of the goblet cells lining the lower two-thirds 

 of the pyloric glands. Indeed, there is direct evidence that gastric mucin can 

 bind histamine (Neugebauer and Schmid, 1949). Like the mast granules this 

 deeper mucin also stains metachromatically with toluidine blue, as does an 

 occasional strand of mucus lying free in the lumen of the stomach, whereas the 

 mucin of the surface cells and most of the secreted mucus stain orthochromatic- 

 ally (blue) with toluidine blue. It is unfortunate that we have as yet no method 

 for fixing the histamine in situ to demonstrate its presence directly by histo- 

 chemical techniques. The association of histamine with the metachromatically- 

 staining mucus is thus at present a matter of inference rather than proof. 

 Nevertheless, it is of interest that here is a site, rich in histamine and yet 

 comparatively poor in mast cells. At present we are at a loss to explain the 

 functional significance of this high concentration of histamine and its regional 

 distribution in the mucosa of the pyloric half of the stomach. 



136 



