Hyperreactivity and 45Ca movements in sensitized guinea-pig tracheal muscle

Responses to KCl and histamine and 45Ca movements were studied in trachea from normal and actively sensitized guinea-pigs. Sensitized tracheas were hyperresponsive and hypersensitive to KCl and histamine. 45Ca uptake experiments show that sensitized tracheal muscle behaves as normal except that the uptake of 45Ca in low concentration (0.03 mM) Ca2+ solution was higher and the number of binding sites for the high affinity component of 45Ca uptake (as estimated by Scatchard-coordinate plot) was augmented. Additionally, in sensitized tracheal muscle, incubation in low (0.03 mM) Ca2+ solution followed by La3+ wash-out resulted in a greater amount of residual 45Ca than in normal tissues. KCl, but not histamine, increased the La3+ resistant 45Ca content. This increase was greater in sensitized than in normal trachea. This demonstrates the existence of hyperreactivity and altered 45Ca movements in sensitized trachealis muscle.