Flow regulation of ecNOS and Cu/Zn SOD mRNA expression in porcine coronaryarterioles

The purpose of this study was to test the hypothesis that increased flow th rough coronary arterioles increases endothelial cell nitric oxide synthase (ecNOS) and Cu/Zn superoxide dismutase (SOD) mRNA expression. Single porcin e coronary arterioles (ID 100-160 mu m; pressurized) were cannulated, perfu sed, and exposed to intraluminal flow sufficient to produce maximal flow-in duced dilation of coronary arterioles (high flow; 7.52 +/- 0.22 mu l/min), low flow (0.84 +/- 0.05 mu l/min), or no flow for 2 or 4 h. Mean shear stre ss was calculated to be 5.7 +/- 1.0 dyn/cm(2) for high-flow arterioles and 1.6 +/- 1.0 dyn/cm(2) for low-flow arterioles. At the end of the treatment period, mRNA was isolated from each vessel, and ecNOS and SOD mRNA expressi on was assessed using a semiquantitative RT-PCR. All data were standardized by coamplifying ecNOS or SOD with glyceraldehyde-3-phosphate dehydrogenase . The results indicate that ecNOS mRNA expression is increased in arteriole s exposed to 2 or 4 h of high flow In contrast, SOD mRNA expression was inc reased only after 4 h of high flow Neither gene is induced by exposure to l ow flow On the basis of these data, we concluded that ecNOS and SOD mRNA ex pression is regulated by flow in porcine coronary arterioles. In addition, we concluded that a threshold level of flow and shear stress must be sustai ned to elicit the upregulation of ecNOS and SOD mRNA expression.