Distribution of mast cells along and across successive segments of the rat digestive tract: a quantitative study.

ABSTRACT

Density of mast cells stained by Alcian Blue at pH 0.3 was measured in the successive segments and the successive layers of rat digestive tract using a semiautomatic computerized image analysis system. The results were calculated in a dual way per area of the entire layer and per area of its connective tissue compartment, in which the mast cells were located (extremely small number of intraepithelial and intramuscular mast cells was not included in the analysis). The distribution of mast cells in the particular layers was rather uniform with exception of the fundus of glandular stomach, where they were located at two distinct levels in the upper quarter of the mucosa and in its lowermost zone, with the layer inbetween being practically free of mast cells. The quantitative estimation of mast cell density in the successive segments of the digestive tract yielded a generally similar profile irrespectively of the way of calculating the results, with the highest overall densities being observed in the middle segments (stomach, jejunum). Especially high densities of mast cells per area unit of the connective tissue were found in the muscularis of glandular stomach and in the lamina propria of small intestine and cecum. The analysis of mast cell density in the successive layers of the particular digestive tract segments revealed no clear pattern when the results were expressed per area unit of the whole layer. Calculation of densities per area unit of the connective tissue showed that lamina propria contained the most numerous mast cells in the entire small and large intestine, moreover, a decreasing pattern of mast cell density across the wall (lamina propria>submucosa>muscularis) was observed in the jejunum, transverse colon and rectum, suggesting that the latter way of calculation more reliably reflects mast cell distribution, which may result from the joint influence of two factors the distance from the lumen of the digestive tract and the density of nerve terminals in its wall.