Endothelium‐dependent relaxations mediated by inducible B1 and constitutive B2 kinin receptors in the bovine isolated coronary artery

• Published in: British journal of pharmacology Vol. 116; no. 5; pp. 2473 - 2481
• Main Authors: Drummond, G.R., Cocks, T.M.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.11.1995; Nature Publishing
• Subjects: Acetylcholine - pharmacology; actinomycin D; Animals; Anti-Inflammatory Agents, Non-Steroidal - pharmacology; Arginine - analogs & derivatives; Arginine - pharmacology; B1, B2 kinin receptors; Biological and medical sciences; Blood vessels and receptors; bovine coronary artery; Bradykinin; Bradykinin - analogs & derivatives; Bradykinin - pharmacology; Bradykinin Receptor Antagonists; Cattle; Coronary Vessels - drug effects; Coronary Vessels - physiology; cycloheximide; des‐Arg9‐[Leu8]‐bradykinin; des‐Arg9‐bradykinin; endothelium; Endothelium, Vascular - physiology; Enzyme Inhibitors - pharmacology; Fundamental and applied biological sciences. Psychology; Hoe‐140; In Vitro Techniques; Muscle Contraction - drug effects; Muscle Contraction - physiology; Muscle Relaxation - drug effects; Muscle Relaxation - physiology; Muscle, Smooth, Vascular - drug effects; Muscle, Smooth, Vascular - physiology; nitric oxide; Nitric Oxide Synthase - antagonists & inhibitors; Nitroarginine; Protein Synthesis Inhibitors - pharmacology; Vertebrates: cardiovascular system; Bovine; Coronary artery; Smooth muscle; In vitro; Endothelium; Vertebrata; Mammalia; Blood vessel; Bradykinin; Nitrogen monoxide; Circulatory system; Artiodactyla; Endothelium derived relaxing factor; Ungulata; Hormonal receptor
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1111/j.1476-5381.1995.tb15098.x

1 Rings of bovine left anterior descending coronary artery (LAD) were contracted with the thromboxane A2‐mimetic, U46619 (1–30 nM), to approximately 40% of their maximum contraction to 125 mM KCl Krebs solution (KPSSmax) for comparison of responses to the B1 and B2 kinin receptor agonists, des‐Arg9‐bradykinin (des‐Arg9‐BK) and bradykinin (BK), respectively. Relaxation responses were normalized as percentages of the initial U46619‐induced contraction level, while contractile responses were expressed as percentages of KPSSmax. 2 After 6 h of in vitro incubation in Krebs solution at 37°C, des‐Arg9‐BK (pEC50, 8.00 ±0.08; maximum response (Rmax), 93.9 ±1.9%) and BK (pEC50, 9.75 ±0.07; Rmax, 100.1 ±0.7%) caused endothelium‐dependent relaxations in precontracted rings of bovine LAD which were competitively and selectively antagonized by the B. receptor antagonist, des‐Arg9‐[Leu8]‐BK (pA2, 6.27 ±0.11) and the B2 receptor antagonist Hoe‐140 (pA2, 9.63 +0.14), respectively. 3 At 3 h of in vitro incubation, the sensitivity (pEC50, 7.45 ±0.10) and Rmax (84.6 ±3.3%) to des‐Arg9‐BK were significantly less than those obtained in the same tissues at 6 h (pEC50, 7.94 ± 0.06; Rmax, 91.4±2.5%), whereas endothelium‐dependent relaxations to BK and ACh were unaffected by incubation time. 4 Relaxation responses to des‐Arg9‐BK, but not BK, at both 3 h and 6 h were significantly attenuated by the protein synthesis inhibitors, cycloheximide (30 and 100 μm) and actinomycin D (2 μm). 5 At 6 h, the nitric oxide (NO) synthase inhibitor, NG‐nitro‐L‐arginine (L‐NOARG, 100 μm), caused a significant 2 fold decrease in pEC50 (9.58 ±0.03) but had no effect on Rmax for BK. For des‐Arg9‐BK, L‐NOARG (100 μm) caused a marked and significant decrease in both the pEC50 and Rmax and revealed contractions to low concentrations of des‐Arg9‐BK. In both cases, L‐NOARG inhibition was reversed in the presence of L‐arginine (10 mM). 6 At 6 h, removal of the endothelium abolished relaxation responses to des‐Arg9‐BK and BK, and for des‐Arg9‐BK, but not BK, unmasked concentration‐dependent contractions (pEC50, 7.57 ±0.09; Rmax, 83.4±9.1%). The sensitivity of contractions to des‐Arg9‐BK increased slightly from 3h (pEC50, 7.37 ±0.08) to 6 h (pEC50, 7.62 ±0.12) of in vitro incubation; however, there was a small but significant depression in the maximum response over this time (Rmax, 126.8 ±8.5% and 103.3 ±8.6% for 3 h and 6 h of incubation respectively). 7 In conclusion, the bovine LAD contains inducible B1 and constitutive B2 endothelial cell kinin receptors, both of which mediate endothelium‐dependent relaxation partly via the release of NO. B1 receptors were also present on the smooth muscle layer of the bovine LAD.