The influence of endorphins on peritoneal and mucosal mast cell secretion
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The histamine-releasing effect of certain opiate drugs prompted a survey of endogenous opiates for mast cell-secretagogue activity. Since intestinal mucosal mast cells (MMC) differ from connective tissue mast cells in their response to a variety of secretagogues and anti-allergic compounds, we have examined the influence of several endogenous opiate peptides on histamine secretion from the two mast cell types in the rat. MMC hyperplasia was induced in rats infected with the nematode Nippostrongylus brasiliensis and MMC were isolated by collagenase digestion from the small intestine. Connective tissue mast cells from the peritoneal cavity (PMC) were isolated by peritoneal lavage. Dynorphin, alpha-neoendorphin, and beta-endorphin had a concentration-dependent secretagogue effect (10(-6)M to 10(-4)M) on PMC that was temperature and energy dependent, but MMC from the same animals were unresponsive to these agents. Differences between PMC and MMC did not appear to be attributable to the MMC isolation procedure since PMC treated similarly remained responsive to endorphin. Endorphin-induced histamine secretion from PMC was partially inhibited by the anti-allergic agent disodium cromoglycate. Inhibition with the opiate antagonist naloxone was nonspecific, occurring only at concentrations that also inhibited antigen-induced mediator release. Mast cell secretion induced by certain opiate peptides may therefore be nonreceptor mediated and relate to a direct membrane effect by basic peptides.
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