Abstract 4171: The Endothelium of Human Internal Mammary Artery Expresses Higher Level of eNOS mRNA and Protein Than That of Radial Artery: Implications in the Long-term Patency
Objectives The internal mammary artery (IMA) has better long-term patency rate than the radial artery (RA) for coronary surgery but the underlying molecular mechanisms are unclear. The present study compared endothelial nitric oxide synthase (eNOS) and related function in these two arteries.
Methods Expression levels of eNOS in the whole tissue, endothelial cells (EC) and smooth muscle cells (SMC) of human IMA and RA were quantified with quantitative real-time PCR (qRT-PCR). The localization of eNOS protein in both IMA and RA was determined by immunohistochemistry (IHC) technique. Cumulative concentration-relaxation curves for acetylcholine (ACh, −10 ~ −4.5 log M) in U46619 -precontraction were also established in these arteries pretreated with/without eNOS inhibitor Nω-nitro-L-arginine (L-NNA, 300μM).
Results qRT-PCR data showed that eNOS mRNA expression level in EC of IMA was significantly higher than that of RA (1.03±0.19 vs. 0.53±0.09, p<0.05, n=7) although it was similar in the integrated vascular tissue with similar ACh-induced relaxations in these two arteries (Rmax: 54.6±6.6% vs. 56.6±7.1%, n=20) that were inhibited by L-NNA (Rmax: 14.7±3.0% for IMA and 15.2±3.2% for RA, p<0.001) or denudation. Accordingly, IHC results demonstrated higher eNOS protein immunoreactivity in EC of IMA than that of RA. In contrast, SMC of IMA expressed lower level of eNOS than that of RA (0.18±0.02 vs. 1.25±0.46, p<0.05, n=7).
Conclusions We have demonstrated that IMA and RA have different expression of eNOS mRNA and protein with higher expression in the EC of IMA than that of RA. This important finding may account for the superior long-term patency rate of the IMA than RA. The present study also provides new insight for gene therapy of those grafting arteries with lower patency rates.