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Bioassay of endothelium‐derived hyperpolarizing factor with abolishment of nitric oxide and the role of gap junctions in the porcine coronary circulation
Author(s) -
Yang Qin,
Ge ZhiDong,
Yang ChengQin,
Huang Yu,
He GuoWei
Publication year - 2003
Publication title -
drug development research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.582
H-Index - 60
eISSN - 1098-2299
pISSN - 0272-4391
DOI - 10.1002/ddr.10137
Subject(s) - apamin , hyperpolarization (physics) , bradykinin , charybdotoxin , endothelium derived hyperpolarizing factor , nitric oxide , chemistry , gap junction , endothelium derived relaxing factor , endothelium , medicine , nitroarginine , nitric oxide synthase , endocrinology , biophysics , pharmacology , potassium channel , biochemistry , stereochemistry , biology , receptor , nuclear magnetic resonance spectroscopy , intracellular
Previous bioassays of endothelium‐derived hyperpolarizing factor (EDHF) were partially related to the residual nitric oxide (NO) resistant to NO synthase inhibitors. Further, the role of gap junctions in EDHF is controversial. We performed a bioassay of EDHF with abolishment of NO production by using the NOS inhibitor N G ‐nitro‐ l ‐arginine ( l ‐NNA) plus the NO scavenger hemoglobin (Hb) and examined the role of gap junctions/K + channels related to EDHF in porcine coronary large and microarteries in an organ chamber/myograph. Bradykinin (BK)‐induced EDHF‐mediated relaxation and hyperpolarization (by a microelectrode) were studied with indomethacin (7 µM), l ‐NNA (300 µM), and Hb (20 µM). NO concentrations ([NO]) were measured electrochemically. In large coronary arteries, BK increased [NO] (9.3±1.7 nM vs. 166.7±18.3 nM, P <0.01) that was significantly reduced by l ‐NNA (49.3±7.8 nM, P <0.01) and eliminated by Hb, and hyperpolarized the downstream endothelium‐denuded artery by 9.0±1.4 mV ( P <0.01) that was reduced but not abolished by l ‐NNA and Hb (5.6±0.7 mV, P <0.01). In microarteries, elimination of NO decreased but did not abolish the hyperpolarization (−63.8±1.5 mV vs. −56.9±1.6 mV, P=0.01) and relaxation (70.2±5.7% vs. 42.3±4.4%, P <0.01). Charybdotoxin (0.1 µM) and apamin (0.5 µM), but neither glybenclimide (3 µM) nor gap junction inhibitors (18α‐glycyrrhetinic acid, 1‐heptanol, and gap 27) reduced the EDHF‐mediated response. We conclude that in porcine coronary arteries, with the abolishment of NO by NOS inhibitors plus the NO scavenger Hb, the non‐NO EDHF exists and is transferable from an endothelium‐intact artery to an endothelium‐denuded artery. Compared with the significant involvement of calcium‐activated K + channels, the gap junctions may only play a minimal role in the EDHF‐mediated response even in the microcirculation of the porcine coronary artery. Drug Dev. Res. 58:99–110, 2003. © 2003 Wiley‐Liss, Inc.