Ischemia-induced coronary collateral growth is dependent on vascular endothelial growth factor and nitric oxide.
BACKGROUND
We hypothesized that ischemia-induced expression of vascular endothelial growth factor (VEGF) and the production of NO stimulate coronary collateral growth.


RESULTS
To test this hypothesis, we measured coronary collateral blood flow and VEGF expression in myocardial interstitial fluid in a canine model of repetitive myocardial ischemia under control conditions and during antagonism of NO synthase. Collateralization was induced by multiple (1/h; 8/d), brief (2 minutes) occlusions of the left anterior descending coronary artery for 21 days. In controls, collateral blood flow (microspheres) progressively increased to 89+/-9 mL. min(-1). 100 g(-1) on day 21, which was equivalent to perfusion in the normal zone. Reactive hyperemic responses (a measure of the severity of ischemia) decreased as collateral blood flow increased. In N(G)-nitro-L-arginine methyl ester (L-NAME)- and L-NAME+nifedipine-treated dogs, to block the production of NO and control hypertension, respectively, collateral blood flow did not increase and reactive hyperemia was robust throughout the occlusion protocol (P<0.01 versus control). VEGF expression (Western analyses of VEGF(164) in myocardial interstitial fluid) in controls peaked at day 3 of the repetitive occlusions but waned thereafter. In sham-operated dogs (instrumentation but no occlusions), expression of VEGF was low during the entire protocol. In contrast, VEGF expression was elevated throughout the 21 days of repetitive occlusions after L-NAME. Reverse transcriptase-polymerase chain reaction analyses revealed that the predominant splice variant expressed was VEGF(164).


CONCLUSIONS
NO is an important regulator of coronary collateral growth, and the expression of VEGF is induced by ischemia. Furthermore, the induction of coronary collateralization by VEGF appears to require the production of NO.
Matsunaga
T
T
Departments of Physiology and Anesthesiology, The Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, USA.
Warltier
D C
DC
Weihrauch
D W
DW
Moniz
M
M
Tessmer
J
J
Chilian
W M
WM
D000818:Animals; D001157:Arterial Occlusive Diseases / Q000150:complications; D015153:Blotting, Western; D003097:Collateral Circulation; D003331:Coronary Vessels; D004285:Dogs; D016228:Endothelial Growth Factors / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006439:Hemodynamics; D006940:Hyperemia / Q000209:etiology; D008222:Lymphokines / Q000378:metabolism*; D008297:Male; D017202:Myocardial Ischemia / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D016228:Endothelial Growth Factors; D004791:Enzyme Inhibitors; D008222:Lymphokines; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester