The contraction induced by calcium ions in isolated guinea-pig vas deferens.

1. When isolated guinea-pig vas deferens was pretreated with 0.01% sodium edetate in an isotonic sucrose medium and then transferred to an edetate-free sucrose medium, the addition of CaCl2 (1.1 to 35.2 mmol/l) induced a contraction. 2. The contraction was greatest when the CaCl2 was added soon after pretreatment with edetate, and decreased with increasing time, almost disappearing after 1 h. 3. When KCl (1.4 to 22.4 mmol/l) was added in place of CaCl2, the contraction was lowest soon after pretreatment with edetate, and increased with time; after 1 h, the effect, was 80.7% of that observed in a preparation that had not been pretreaated with edetate.