Abstract

The influence of the epithelium on contractions and histamine release evoked by ovalbumin and d-tubocurarine has been examined in guinea pig superfused tracheal strips under several experimental conditions. Without drug pretreatment, removal of the epithelium resulted in larger (P < .05) total histamine released by ovalbumin, 10(-4) to 10(-1) mg/ml, and by d-tubocurarine, 3 x 10(-3) M. In the presence of indomethacin, 5 x 10(-6) M, epithelium removal resulted in elevated histamine release only at smaller ovalbumin concentrations, 10(-4) and 10(-3) mg/ml. Indomethacin did not change the influence of the epithelium on histamine release by d-tubocurarine. Indomethacin treatment abolished the influence of the epithelium on ovalbumin-induced tracheal contraction. With indomethacin, larger (P < .05) histamine release was seen with ovalbumin, 10(-1) and 1 mg/ml, when the epithelium was intact. The larger histamine release in response to ovalbumin, 10(-1) mg/ml, in the presence of the epithelium was unaltered by pyrilamine, 10(-6) M, cimetidine, 10(-4) M, and thioperamide, 10(-6) M, to block histamine H1, H2 and H3 receptors, respectively. Therefore, histamine released by ovalbumin does not stimulate histamine release through an action on these receptors when the epithelium is intact. In the presence, but not in the absence, of the epithelium, A64077, 10(-5) M, and ICI198615, 10(-8) and 10(-6) M, inhibitors of 5-lipoxygenase and LTD4/E4 receptors, respectively, inhibited histamine release by ovalbumin, 10(-1) mg/ml. Histamine release by ovalbumin, 10(-4) mg/ml, and d-tubocurarine, 3 x 10(-3) M, studied with or without epithelium was not altered by A64077 or ICI198615.(ABSTRACT TRUNCATED AT 250 WORDS)