The action of angiotensin on the human colon in vitro.

1. The action of angiotensin on the circular and longitudinal muscle of the human colon has been studied in vitro. The ED50 value (g/ml) of circular muscle was 8.7 x 10(-8) and of longitudinal muscle 3.1 x 10(-8), while the corresponding figures for acetylcholine were 1.6 x 10(-6) and 1.1 x 10(-6), respectively. Angiotensin caused a sustained contraction associated with prolonged tachyphylaxis.2. As the action of angiotensin was not antagonized by atropine, hexa-methonium or procaine, angiotensin appeared to act directly on the smooth muscle of the human colon.3. Lidoflazine is not a specific antagonist of angiotensin.