Functional heterogeneity of human mast cells from different anatomic sites: in vitro responses to morphine sulfate

The responses of human cutaneous, pulmonary, intestinal, and cardiac tissue mast cells to the histamine-releasing agent morphine sulfate (MS) were investigated in vitro. Human cutaneous mast cells released significant amounts of histamine in the presence of 1 to 100 mumol/L concentrations of MS. Histamine release was detectable within 5 minutes after challenge and was complete by 15 minutes. A maximal histamine release of 21.6% (+/- 1.4 SEM) was observed after stimulation with 100 mumol/L of MS. This MS effect was inhibited by the opiate receptor antagonist naloxone with a 59% inhibition detected at equimolar concentrations and an 88% inhibition occurring in the presence of a tenfold molar excess of naloxone. Naloxone did not alter the cutaneous mast cell response to the calcium ionophore A23187. Human mast cells derived from pulmonary, intestinal, and cardiac tissues, as well as blood basophils, did not release histamine after stimulation with 1 to 200 mumol/L of MS, whereas each of these cell preparations responded to an IgE-mediated stimulus. The results of this study demonstrate that cutaneous mast cells release inflammatory mediators after stimulation by MS, whereas mast cells residing in lung, heart, and gastrointestinal tissues do not. These observations indicate that human mast cells in different anatomic sites can vary in their functional responses.