Submitted on September 13, 2002
Accepted on December 10, 2002
Influence of coronary artery diameter on eNOS protein content
Maurice H. Laughlin1*, James R. Turk2, William G. Schrage3, Chris R. Woodman4, and Elmer M. Price4
1 Department of Biomedical Sciences, University of Missouri, Columbia, MO, USA; Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA; Department of Medical Physiology, University of Missouri, Columbia, MO, USA
2 Department of Biomedical Sciences, University of Missouri, Columbia, MO, USA
3 Department of Medical Physiology, University of Missouri, Columbia, MO, USA; Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
4 Department of Biomedical Sciences, University of Missouri, Columbia, MO, USA; Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
* To whom correspondence should be addressed. E-mail: laughlinm{at}missouri.edu.
The purpose of this study was to test the hypothesis that the content of endothelial nitric oxide synthase (eNOS) protein (eNOS protein/g total artery protein)increases with decreasing artery diameter in the coronary arterial tree. Content of eNOS protein was determined in porcine coronary arteries with immunoblot analysis. Arteries were isolated in six size categories from each heart: Large arteries (301 - 2,500 µm internal diameter (ID), small arteries (201 - 300 µm ID), resistance arteries (151 - 200 µm ID); large arterioles (101-150 µm ID), intermediate arterioles (51-100 µm ID), and small arterioles(< 50 µm ID). To obtain sufficient protein for analysis from small and intermediate sized arterioles, 5-7 arterioles 1 to 2 mm in length were pooled into one sample for each animal. Results establish that the number of smooth muscle cells per endothelial cell decreases from 10 to 15 in large coronary arteries to 1 in the smallest arterioles. Immunohistochemistry revealed that eNOS is located only in endothelial cells in all sizes of coronary artery and in coronary capillaries. Contrary to our hypothesis, eNOS protein content did not increase with decreasing size of coronary artery. Indeed, the smallest coronary arterioles had less eNOS protein/gram of total protein than the large coronary arteries. These results indicate that eNOS protein content is greater in the endothelial cells of conduit arteries, resistance arteries, and large arterioles than in small coronary arterioles.
