Functional differences between human cutaneous mast cells and basophils: a comparison of morphine-induced histamine release

Intravenous administration of morphine sulfate often produces urticarial and hypotensive reactions associated with elevations in plasma histamine. The source of this histamine and mechanisms controlling its release are poorly understood. Previous studies of morphine-induced histamine release compared human leukocytes to rat peritoneal mast cells. The effects of morphine on human cutaneous mast cells has not been examined. We studied in vitro histamine release from human basophils and human skin preparations containing cutaneous mast cells to evaluate their relative, contribution to the pharmacologic effects of morphine. Human skin mast cell preparations showed dosedependent histamine release over a morphine concentration range of 1.5×10^-5 to 4.5×10^-3M, with peak release occurring at 5×10^-4M, with peak release occurring at 5×10^-4M. Clinically, morphine sulfate is usually injected as a 1.5×10^-2M solution. Histamine release was calcium dependent and equivalent to that obtained with 3 and 10 m M strontium. Morphologic examination revealed degranulation and exocytosis occurring in morphine-stimulated tissue but not in specimens exposed to buffer alone. Lactate dehydrogenase levels did not increase following morphine incubation, thus supporting a noncytolytic mechanism of histamine release. Basophils, in contrast, showed no significant histamine release from exposure to morphine up to 10^-2M. Concanavalin A, as a positive control in these same preparations, produced a mean histamine release of 21.0%. Our studies indicate distinct functional differences between human skin mast cell and human blood basophil responses to morphine sulfate. We conclude that the cutaneous and systemic reactions to morphine sulfate probably result from the release of histamine from mast cells rather than from basophils.