Figure 2.

(a) Original experimental record showing the contractile effect of human U-II in rat isolated left anterior descending coronary artery. Vertical lines denote addition of drugs at the concentrations indicated. Note that the addition of carbachol shows this to be an endothelium-intact vessel, and also that some relaxant effects were observed at high concentrations of human U-II (100 and 1000 nM). (b) Contractile and relaxant effects of human U-II in rat isolated left anterior descending coronary artery. Data (presented as mean±s.e.mean) above zero indicate the contractile effects of the peptide in resting arteries, whilst the data below zero denote the relaxant effects of human U-II in 5-HT-precontracted vessels. Data were fitted to the logistic equation and the parameters are given in the text. (c) Original experimental record showing the relaxant effect of human U-II in rat isolated coronary artery precontracted with 5-HT (3 μM). Vertical lines denote addition of drugs at the concentrations indicated. Note that the addition of carbachol shows this to be an endothelium-intact vessel, and also that some contractile effects were observed at high concentrations of human U-II (above 100 nM). The apparent ‘stepped' nature of the tension responses is due to a lack of resolution in the recording system at the high gain required to measure these small responses.