Role of NO and EDHF-mediated endothelial function in the porcine pulmonary circulation: comparison between pulmonary artery and vein.
OBJECTIVE
To compare electrophysiological measurement of nitric oxide (NO) release and endothelium-derived hyperpolarizing factor (EDHF)-mediated endothelial function in porcine pulmonary arteries and veins.


METHODS
Isolated pulmonary interlobular arteries (PA) and veins (PV) were obtained from a local slaughterhouse. By using a NO-specific electrode and a conventional intracellular microelectrode, the amount of NO released from endothelial cells and hyperpolarization of smooth muscle cells were investigated. The bradykinin (BK)-induced relaxation in the precontraction by U(46619) was examined in the absence or presence of N(G)-nitro-l-arginine (l-NNA), indomethacin (INDO) plus oxyhemoglobin (HbO).


RESULTS
The basal release of NO was 7.0+/-1.2 nmol/L in PA (n=8) and 5.5+/-1.6 nmol/L in PV (n=8, p<0.01). BK-induced release of NO was 160.4+/-10.3 nmol/L in PA (n=8) and 103.0+/-14.7 nmol/L in PV (n=8, p<0.001) with longer releasing duration in PA than in PV (14.3+/-1.3 vs. 12.1+/-0.8 min, p<0.01). BK evoked an endothelium-dependent hyperpolarization and relaxation that were reduced by l-NNA, INDO, and HbO (hyperpolarization: 12.8+/-1.3 vs. 8.0+/-1.4 mV in PA, n=6, p<0.001 and 8.3+/-1.4 vs. 3.0+/-0.8 mV in PV, n=6, p<0.001; relaxation: 92.8+/-3.1% vs. 19.6+/-11.1% in PA n=8, p<0.001 and 70.3+/-7.9% vs. 6.0+/-6.8% in PV, n=8, p<0.001). Both hyperpolarization (8.0+/-1.4 vs. 3.0+/-0.8 mV, p<0.001) and relaxation (19.6+/-11.1% vs. 6.0+/-6.8%, p<0.01) were greater in PA than in PV.


CONCLUSIONS
Both NO and EDHF play an important role in regulation of porcine pulmonary arterial and venous tones. The more significant role of NO and EDHF is revealed in pulmonary arteries than in veins.
Zhang
Rong-Zhen
RZ
Department of Surgery, The Chinese University of Hong Kong, Block B, Prince of Wales Hospital, Shatin, N.T., Hong Kong SAR, China.
Yang
Qin
Q
Yim
Anthony P C
AP
Huang
Yu
Y
He
Guo-Wei
GW
D000818:Animals; D001685:Biological Factors / Q000378:metabolism*; D001920:Bradykinin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008564:Membrane Potentials; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D009569:Nitric Oxide / Q000378:metabolism*; D011651:Pulmonary Artery / Q000187:drug effects / Q000378:metabolism*; D011667:Pulmonary Veins / Q000187:drug effects / Q000378:metabolism*; D013552:Swine; D013997:Time Factors; D014664:Vasodilation; D014665:Vasodilator Agents / Q000494:pharmacology
D001685:Biological Factors; D014665:Vasodilator Agents; C067410:endothelium-dependent hyperpolarization factor; D009569:Nitric Oxide; D001920:Bradykinin