Expression of vascular endothelial growth factor and its receptors is increased, but microvascular relaxation is impaired in patients after acute myocardial ischemia

Background: Vascular endothelial growth factor, a specific endothelial mito gen, plays an important role in myocardial angiogenesis. Previous work has demonstrated increased expression of vascular endothelial growth factor and its receptors in a rat myocardial infarction model, as well as in a pig mo del of chronic ischemia. The expression of vascular endothelial growth fact or and other growth factors after acute myocardial ischemia in patients has not been examined. In this study We examined the expression of vascular en dothelial growth factor and its receptors and the responsiveness of human a trial microvessels to vascular endothelial growth factor before and after a cute ischemia. Methods: Paired specimens of human atrial tissue were harvested before and after atrial devascularization (ligation) in 16 patients undergoing coronar y bypass operations. Results: The messenger RNA (reverse transcriptase-polymerase chain reaction ) level of vascular endothelial growth factor and vascular endothelial grow th factor receptor 1 were increased by 22.2% +/- 4.2% and 30.7% +/- 7.6%, r espectively (P < .05), in the ischemic specimens as compared with the contr ol specimens. Protein expression (Western blotting) of vascular endothelial growth factor and that of vascular endothelial growth factor receptor 1 al so were increased significantly by 71.7% <plus/minus> 27.8 and 68.2% +/- 27 .6%, respectively (P < .05). However, both RNA and protein expressions of a nother vascular endothelial growth factor receptor, vascular endothelial gr owth factor receptor 2, and fibroblast growth factor and fibroblast growth factor receptor 1 were unchanged. Reactivity of precontracted atrial vessel s was examined with video microscopy. Vascular endothelial growth factor-in duced (33.9% <plus/minus> 2.4% vs 18.3% +/- 2.8% in control and ischemic ve ssels, respectively; P < .05), fibroblast growth factor-induced (31.6% <plu s/minus> 3.2% vs 15.8% +/- 4.1%, P < .05), and substance P-induced (84.5% < plus/minus> 3.7% vs 54.3% +/- 9.0%, P < .05) microvascular relaxations were decreased in ischemic samples and in the presence of N(G)nitro-L-arginine, whereas responses to sodium nitroprusside were unchanged (90.9% <plus/minu s> 2.2% vs 91.2% +/- 2.0%). Conclusions: This study suggests that acute myocardial ischemia in patients results in increased expression of vascular endothelial growth factor but not fibroblast growth factor and that the functional activity of vascular e ndothelial growth factor receptors and that of other growth factors may be impaired.