Effects of cod bradykinin and its analogs on vascular and intestinal smooth muscle of the Atlantic cod, Gadus morhua

The effects of [Arg(0),Trp(5),Leu(8)]-BK (cod [Arg(0)]BK) on vascular prepa rations from branches of the cod celiac artery and on longitudinal smooth m uscle preparations from the cod intestine were investigated. Cod [Arg(0)]BK (3 x 10(-8) M) caused a relaxation of the celiac artery precontracted with adrenaline. The relaxation was abolished by the cyclooxygenase inhibitor i ndomethacin, suggesting that the effect is mediated through the release of prostaglandins, but there was no evidence for the involvement of leukotrien es or nitric oxide in the response. In the intestinal preparations, cod [Ar g(0)]BK produced concentration-dependent contractions (pD(2) = 8.28 +/- 0.1 6). Experiments with N-terminally and C-terminally truncated analogs and wi th alanine-substituted analogs of cod [Arg(0)]BK demonstrate that the centr al amino acid Gly(4) and the C-terminal amino acids Leu(8) and Arg(9) are t he most important in determining the conformation of the peptide that inter acts with the receptor. The results indicate that the ligand binding proper ties of the cod BK receptor are considerably different from the receptor pr esent in trout tissues and may resemble those of the mammalian B-2 receptor more closely. (C) 2001 Elsevier Science Inc. All rights reserved.