A further investigation into the energy dependence of angiotensin II-induced contractions of isolated smooth muscle preparations.

1 The energy dependence of angiotensin and acetylcholine-induced contractions of rat descending colon and uterus was investigated. 2 Differences were observed in the effect of anaerobic substrate depletion upon responses of colon and oestrous and dioestrous uterus. These were attributed to differences in the energy metabolism of the tissues and were correlated with differences in tissue levels of glycogen. 3 The preferential reduction of angiotensin responses of dioestrous uterus and descending colon when exposed to 2,4-dinitrophenol, was evidence for an energy dependent stage in the angiotensin response distinct from the contraction process itself. 4 The absence of a preferential reduction of the angiotensin response of oestrous uterus when exposed to 2,4-dinitrophenol appeared to be related to the ability of this tissue to generate ATP by anaerobic glycolysis. 5 It was concluded that the energy for the angiotensin response may be derived either anaerobically or aerobically, depending upon the tissue.