A quantitative cytochemical study of the growth of individual mast cells.

For individual mast cells, relationships between their dry mass and their content of heparin and 5-hydroxytryptamine (5-HT) were studied. This was achieved by measuring these parameters successively on identical cells, by means of quantitative cytochemical techniques. The peritoneal mast cells have a very long life span and a slow turnover of granule components. Increase of the dry weight of the cells may therefore be taken as an expression of cellular growth. Mast cell populations from younger and older animals were analysed in an attempt to evaluate the influence of cell-aging and animal-aging on the growth of the mast cells. The analysis was based on allometric (log-log) plots and linear regressions. Within the cell populations there were strong mutual correlations between the cell parameters studied, without any obvious deviations from linearity. However, the slopes of the allometric lines indicated a somewhat different mode of growth for mast cell from younger and older animals. The capacity of the mast cells to accumulate 5-HT after a single injection of its precursor, 5-hydroxytryptophan, was used as a functional test. In relation to the cell weight, the induced increase of 5-HT was greater for lighter than for heavier mast cells. This difference between light and heavy mast cells was greater for cells from younger than from older animals. These differences in growth and functional properties between mast cells from younger and older animals were interpreted as an effect of the animals rather than of aging of the cells.