Histamine release by compound 48/80: Evidence for the depletion and repletion of calcium using chlortetracycline and45calcium

Abstract

Selective release of histamine from rat peritoneal mast cellsin vitro was induced by compound 48/80 (1 μg/ml). Most of the release (75–80%) occurred in a calcium(Ca)-free medium but optimum release was obtained in the presence of 0.9 mM Ca. The release in Ca-free medium still occurred after 180 min incubation. However, prolonged incubation (180 min) in a medium containing chelating agents (EDTA or EGTA) resulted in complete inhibition of histamine release, loss of fluorescence seen with chlortetracycline (CTC) and loss of previously loaded⁴⁵Ca from the mast cells. Addition of Ca to these cells resulted in rapid restoration of fluoresence with chlortetracycline. There was also a rapid uptake of⁴⁵Ca. Partial depletion of cellular Ca (60 min incubation with EDTA) reduced the rate as well as the amount of histamine release by compound 48/80. These data provide direct evidence for the depletion of cellular Ca which is utilized by compound 48/80 to induce histamine release.