Allometric growth of the rat peritoneal mast cell mass and of the granular constituents: heparin, histamine and 5-hydroxytryptamine.

This paper reports an attempt to measure the normal growth of connective tissue mast cells in rats aged 6 to 24 weeks. We used peritoneal mast cells as a model, and calculated the total mast cell mass and the mass of its components from total peritoneal mast cell numbers and their content of protein, heparin, histamine and 5-hydroxytryptamine (5-HT). The growth process was analysed with the aid of allometric, log-log plots of mast cell quantities versus body weight and linear regression, in order to facilitate comparisons with other systems, notably the lymphoid apparatus. We found that the growth of peritoneal mast cells conformed to the allometric principle (r = 0.91 to 0.93). There were no deviations from linearity or changes in the slope (growth rate constant, k) of the allometric lines within the studied growth interval. K ranged from 1.3 to 1.7, indicating that the mast cell mass and its different components grew at a faster rate than the body as a whole, typical of a late maturing cell system. The mode of growth of the peritoneal mast cells is thus distinctly different from that of the lymphoid system, and neither thymus involution nor sexual maturation appears to influence the growth of these cells.