A Cytofluorometric Analysis of Polymer-Induced Mast Cell Secretion

Abstract

Quantitative cytofluorometry was used to study the mechanism of mast cell secretion induced by polymyxin B <i>in vitro. </i>We measured 5-hydroxytryptamine (5-HT) and heparin in mast cells and individual mast cell granules, extruded from the cells or obtained from the interior of the cells by micromanipulation. Mast cell granules of untreated control cells contained both 5-HT and heparin. After polymyxin stimulation both intracellular and extruded mast cell granules contained heparin, but some intracellular and all extruded granules lacked 5-HT. These results indicate that the mast cell amines may be released from granules while they are still within the cellular domain. The mast cell granules did not release heparin whether extruded from the cell or not. The release of heparin from mast cells was thus determined by the number of extruded granules. Our results further suggest that the granules first released are those situated in the periphery of the cell and contain the largest quantities of amines and heparin. In agreement with the granule measurements, fluorescence measurements on stimulated mast cells showed a dose-dependent decrease of both heparin and 5-HT, but the 5-HT content decreased proportionally more than that of heparin.