Ultrastructural observations on mast cell degranulation and its prevention.

The surface alterations of rat peritoneal mast cells during degranulation induced by calcium chloride (CaCl2) and its prevention by salbutamol sulfate (Sal. Sulf.), chlorpheniramine maleate (CM), and disodium cromoglycate (DSCG) were followed with a scanning electron microscope. CaCl2 caused a protuberation of the cytoplasmic granules already after 30 s, an advanced degranulation after 60-75 s, and a complete destruction of the cells after 180 s of incubation. The degranulation process was prevented by Sal. Sulf., CM, and DSCG. A comparison of the surface changes induced by these agents with the ultrastructural findings observed with a transmission electron microscope showed that neither Sal. Sulf. nor CM prevented the alterations of the internal structure of the cells, suggesting that these substances act mainly on the cytoplasmic membrane. The best prevention for both the surface and the internal structure of the cells was obtained by DSCG, indicating that this substance is a stabilizer of both membrane and internal organelles of the mast cells.