Cumulative concentration-response curves to (a) thrombin, (b) trypsin, (c) SFLLRN and (d) SLIGRL in pig coronary artery ring preparations contracted to ∼50% of their maximum contraction with U46619 in the absence (control) and presence of nifedipine (0.3 μM), nifedipine and K+ (67 mM), nifedepine and L-NOARG (100 μM) or nifedipine plus K+ and L-NOARG. Each point represents the mean±s.e.mean of six (a, b, c) and three (d) experiments. *Denotes Rmax and pEC50 values significantly different from control (P<0.05).