The effect of contraction and Ca2+ removal on the indomethacin-induced increase in tracheal smooth muscle reactivity.
The effect of contraction and Ca2+ on the indomethacin mediated increased tracheal reactivity to histamine was studied in swine isolated tracheal smooth muscle. The potentiating effect of indomethacin was not directly related to the size of muscle contraction. Histamine, but not acetylcholine-induced contractions were partially inhibited in a zero-Ca2+ Krebs solution and almost abolished in zero-Ca2+ Krebs solution containing 0.1 mM EGTA. Indomethacin potentiated histamine but not acetylcholine-induced contractions in the zero-Ca2+ medium. Re-addition of Ca2+ ions caused a further potentiation of the histamine-induced response. The histamine response with indomethacin when EGTA was present was further reduced. Indomethacin had no effect on Ca2+-contractures of tissues bathed in zero-Ca2+ solution containing 80 mM K+. The results demonstrate that histamine-induced tone is largely dependent on labile Ca2+, whereas its potentiation by indomethacin, is only partly dependent on this cation pool.
D000818:Animals; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D004533:Egtazic Acid / Q000494:pharmacology; D006632:Histamine / Q000494:pharmacology; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects*; D013552:Swine; D014132:Trachea / Q000187:drug effects*
D004533:Egtazic Acid; D006632:Histamine; D002118:Calcium; D007213:Indomethacin