[Effects of epithelium removal and cooling on tracheal contraction in guinea pigs]

We investigated the effects of epithelium removal and cooling (32 degrees C, 27 degrees C, 22 degrees C) on isolated tracheal smooth muscle contraction induced by bethanechol (BCh), acetylcholine (ACh), histamine (Hist), and KCl in guinea pigs. The pD2 values (-logED50) increased in the epithelium damaged group compared with the intact group when ACh was administered at 37 degrees C, 32 degrees C, 27 degrees C and 22 degrees C, with histamine at all four temperature conditions, and with KCl at 37 degrees C, 32 degrees C and 27 degrees C. In both groups, the pD2 values for BCh, ACh, and KCl tended to decrease as temperature was lowered, and significant decrease in pD2 was observed at 27 degrees C. In contrast, the pD2 value for histamine tended to increase as temperature was lowered in every group. Concerning these agents, we conclude that epithelium removal and cooling exert neither significant nor consistent effect on tracheal epithelial function.