5-hydroxytryptamine content of mast cells, mast cell numbers and body growth

Abstract

The 5-Hydroxytryptamine (5-HT) content of peritoneal mast cells was studied in relation to body growth in male albino rats. The study was performed during the period of rapid body growth between 40 and 190 days of age, under controlled environmental conditions. Mean mast cell 5-HT content was calculated after extraction and fluorometric assay of 5-HT from peritoneal cell suspensions. The 5-HT content of individual cells within the mast cell populations was quantitated with a sensitive cytofluorometric procedure. The two methods showed excellent agreement with each other. A strong correlation between mast cell 5-HT content and both age and body weight was found. The relation to age was markedly curved while the relation to body weight was almost linear within the range of body weights studied. There was a 5-fold increase in mean mast cell 5-HT content, from approx. 0.2 pg/cell at 40 days of age (body weight around 175 g) to about 1 pg/cell at 190 days of age (body weight around 550 g). During the same period of time the number of mast cells in the peritoneal cavity increased from about 1 to 3.5 million cells. The 5-HT content of individual mast cells appeared to be log-normally distributed within the mast cell populations of both young and old rats. All populations studied were unimodal without signs of specific subpopulations. Together with available evidence concerning the proliferation kinetics of mast cells, the results suggest that aging mast cells accumulate 5-HT.