Disodium cromoglycate inhibition of substance P-induced histamine secretion is calcium dependent

Histamine secretion was induced by substance P, in a dose-dependent manner, from rat peritoneal mast cells, both in the presence and absence of Ca²⁺ in the medium, and disodium cromoglycate (DSCG) produced a dose-dependent inhibition of the histamine secretion in Ca²⁺-containing medium. However, in the absence of Ca²⁺, DSCG was ineffective or had a far weaker activity. Mg²⁺, Sr²⁺ and Ba²⁺ were ineffective in restoring the DSCG activity when added to medium devoid of divalent metal ions. Therefore, extracellular Ca²⁺ seems to be a specific requirement for the binding of DSCG to its 'receptors' on the mast cell surface or some steps in the DSCG action.