Angiotensin II stimulates human gastric smooth muscle in vitro

1. For a precise analysis of angiotensin II (ANG) effects on human gastric muscle, we dissected longitudinal (lo) and circular (ci) strips from fundus (Fu), corpus (Co) and antrum (An), and circular muscle from the inner and outer part of the pyloric sphincter (Py-inn and Py-out) and from duodenum. The mechanical activity of these muscle strips was recorded simultaneously under auxotonic conditions. Preparations were taken from a total of 10 stomachs (from organ donors or gastrectomy preparations). 2. Excitatory effect after application of ANG (10(-9) to 10(-6) mol l-1) were regularly observed in all types of preparation (threshold: 10(-9) mol/l). 3. The quality of the responses depended on the general characteristics of the type of preparation. Tonic types of muscle showed predominantly tonic responses to ANG (Fu-lo, Fu-ci, Co-lo). Purely phasic muscles (An-ci) showed increases of the phasic activity (amplitude up to 33% delta 1). Intermediate types of muscle exhibited combined phasic/tonic responses (Co-ci, An-lo). Phasic responses were also seen in Py-out. Inner pyloric muscle (Py-inn) responded only to a small extent to ANG. Phasic/tonic activations were observed in the duodenal preparations, accompanied by slight increases in frequency. 4. The intensity of the ANG-induced responses often exceeded the maximum acetylcholine-induced activation. The qualitative pattern of ANG responses was similar to that of bombesin-induced activation.