NON-MAST CELL HISTAMINE 



the largest cells being related to the vessels which traverse the middle of the 

 submucosa. A few similar, though smaller, mast cells accompany the loose 

 connective tissue upwards between the tubular pyloric glands. In view of the 

 obvious differences in mast-cell content of mucosa and submucosa, it was of 

 interest to determine the relative values for histamine in these two layers. 



Mast cells were counted in the paraffin sections, using a binocular Watson 

 microscope of standard tube length, eye-piece x 8, and objective x 50, giving 

 a final magnification of 600 diameters. Figure 53 records the average number 

 of mast cells per twenty fields at each of eleven levels, from the surface of the 



A HISTAMINE 



s*y 



>|<- SUBMUCOSA- 



Fig. 52 



Histamine values (A) and mast-cell contents (B) at various depths in 

 the mucosa and submucosa of hog pylorus. It is clear that the 

 sharp inflection in each curve occurs at a different level. Something 

 other than mast cells is binding histamine in the deeper mucosa. 



mucosa to the base of the submucosa. The underlying muscle was not examined 

 in detail since preliminary observations had shown it to contain very few mast 

 cells and very little histamine. 



Histamine was estimated in frozen sections at eight levels in depth of 

 the combined mucosa and submucosa (Fig. 52). Fresh tissue, stripped of its 

 muscle, was cut, parallel to the surface, on the freezing microtome after the 

 manner of Feldberg and Harris (1953), each tissue slice being then rapidly 

 weighed and placed in 10 per cent trichloracetic acid for the extraction of its 

 histamine. The subsequent assays were carried out either on the standard 

 guinea pig ileum preparation or on the blood pressure of the atropinized cat. 



Results. If we consider first the findings for the submucosa, we see that 

 the high mast-cell content (average, eighteen cells per field) has its counterpart 

 in a correspondingly high value for histamine (average, 97 [xg./g.). This is in 



135 



