Effects of Calcium and Phosphatidyl Serine in Rat Mast Cell Reaction to Dextran

Abstract

Summary

Histamine release from Sprague–Dawley rat mast cells by dextran was completely inhibited by the absence of exogenous Ca²⁺ (in contrast to release from the same cells by antigen). Also, spontaneous leakage of histamine from the cells increased in the absence of Ca²⁺, and cell responsiveness was not completely restored by readding Ca²⁺. We found no effective substitute for Ca²⁺ in the release reaction. Ca²⁺ was not maximally effective immediately when added back to Ca-deficient cells, but almost the full effect of diluting Ca²⁺ in the medium (which decreased release) and of adding PS (which increased release) were very rapidly established, suggesting that both Ca²⁺ and PS might act (in part) at superficial cell sites. Release from activated cells could be stopped short by adding glucose or by diluting the cell-dextran mixture with normal buffer, as well as by adding EDTA, which deserves further study.