THE EFFECT OF EDTA ON CONTRACTILE RESPONSES OF GUINEA-PIG TRACHEA IN CALCIUM-FREE MEDIUM AND ON THE RECOVERY OF THE CONTRACTILE RESPONSES IN CALCIUM-CONTAINING SOLUTION

1. Acetylcholine (0.1 mmol/l) and KCl (80 mmol/l) induce contractile r esponses in guinea-pig trachea. 2. In the absence of extracellular Ca, contractile responses to ACh or KCl decrease as the preincubation tim e or the EDTA concentration increases. 3. Exposure of the tissue to Ca -free medium decreases the basal tone. 4. Prolonged incubation in the presence of EDTA (1 mmol/l) promotes a delay in the recovery of the to nic component of the contraction elicited subsequently by acetylcholin e and KCI in physiological salt solution, and abolishes the phasic one .