This Article Full Text Full Text (PDF) All Versions of this Article: biophysj.107.120626v1 94/5/1880    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Liu, X. Articles by Friedman, A. PubMed PubMed Citation Articles by Liu, X. Articles by Friedman, A.

Nitric Oxide Diffusion Rate is Reduced in the Aortic Wall

Xiaoping Liu ^*, Parthasarathy Srinivasan , Eric Collard ^*, Paula Grajdeanu , Jay L. Zweier ^* and Avner Friedman 

^* Davis Heart and Lung Research Institute, Division of Cardiovascular Medicine, Department of Internal Medicine, Department of Biomedical Engineering, and Mathematical Biosciences Institute, Ohio State University, Columbus, Ohio

Correspondence: Address reprint requests to Xiaoping Liu, Tel.: 614-292-1305; E-mail: xiaoping.liu{at}osumc.edu.

Endogenous nitric oxide (NO) plays important physiological roles in the body. As a small diatomic molecule, NO has been assumed to freely diffuse in tissues with a diffusion rate similar to that in water. However, this assumption has not been tested experimentally. In this study, a modified Clark-type NO electrode attached with a customized aorta holder was used to directly measure the flux of NO diffusion across the aortic wall at 37°C. Experiments were carefully designed for accurate measurements of the apparent NO diffusion coefficient D and the partition coefficient in the aortic wall. A mathematical model was presented for analyzing experimental data. It was determined that = 1.15 ± 0.11 and D = 848 ± 45 µm²/s (n = 12). The NO diffusion coefficient in the aortic wall is nearly fourfold smaller than the reported diffusion coefficient in solution at 37°C, indicating that NO diffusion in the vascular wall is no longer free, but markedly dependent on the environment in the tissue where these NO molecules are. These results imply that the NO diffusion rate in the vascular wall may be upregulated and downregulated by certain physiological and/or pathophysiological processes affecting the composition of tissues.