Fig. 9. Tension recordings from the intestinal vein showing the vasodilatory effect of the calcium ionophore, A23187 (A), and its effect in the presence of the cyclo-oxygenase inhibitor, indomethacin (B), and in the absence of an intact endothelium (C). Vessels were pre-incubated with indomethacin (10^–5 mol l^–1) for approximately 10 min prior to being constricted with endothelin-1 (ET-1; 10^–8 mol l^–1), and at the point of maximal vasoconstriction, the ionophore (3x10^–6 mol l^–1) was added. Pre-incubation with indomethacin or disruption of the endothelium abolished the dilation induced by the addition of the ionophore (3x10^–6 mol l^–1; N=3).