AN EPITHELIAL-DEPENDENT CONTRACTING FACTOR INDUCED BY CALCIUM INFLUX IN GUINEA-PIG TRACHEA

The effects of epithelium removal were studied on the contraction induced by Ca2+ in K+-depolarizing solution, and by the calcium ionophore A 23187 in guinea-pig isolated tracheal strips. Epithelium removal reduced the maximal response to Ca2+ in K+-depolarizing solution and caused a significant shift to the right of the Ca2+ concentration-response curves. The contraction induced by the calcium ionophore A 23187 (10-6 M) was also markedly reduced by epithelium removal. These results suggest the occurrence of an epithelium-derived contracting factor. The effects of hexamethonium, atropine, spantide and thiorphan showed that acetylcholine and neurokinins play a minor role in the Ca2+-induced contraction. The epithelium-dependent potentiation of the calcium- and of the A 23187-induced contractions was inhibited by an antibody selective for rat calcitonin gene-related peptide (rCGRPα). Therefore, CGRP-like immunoreactive material may be part of the epithelium-dependent contracting factor of guinea-pig trachea. Comparison of concentration-response curves for rCGRPα in epithelium-free and in intact guinea-pig tracheal strips suggests that an epithelium-dependent contracting factor may be mobilized by CGRP. © 1993 Academic Press.