Submitted on March 14, 2008
Accepted on June 11, 2008
Cardiac norepinephrine transporter (NET) protein expression is inversely correlated to chamber norepinephrine content
Erica A. Wehrwein1, Lindsay M. Parker1, Anna A. Wright1, John M Spitsbergen2, Martin Novotny3, Dagmar Babankova3, Greg M Swain3, Beth A. Habecker4, and David L. Kreulen1*
1 Physiology, Michigan State University, East Lansing, Michigan, United States
2 Biological Sciences, Western Michigan University, Kalamazoo, Michigan, United States
3 Chemistry, Michigan State University, East Lansing, Michigan, United States
4 Physiology & Pharmacology, Oregon Health & Science University, Portland, Oregon, United States
* To whom correspondence should be addressed. E-mail: dkreulen{at}msu.edu.
The cardiac neuronal norepinephrine (NE) transporter (NET) in sympathetic neurons is responsible for uptake of released NE from the neuroeffector junction. The purpose of this study was to assess the chamber distribution of cardiac NET protein measured using [3H]nisoxetine binding in rat heart membranes and correlate NE content to NET amount. In whole mounts of atria NET was colocalized in nerve fibers with tyrosine hydroxylase (TH) immunoreactivity. NE content expressed as µg NE/gram tissue was lowest in the ventricles however NET binding was significantly higher in the left ventricle than the right ventricle and atria (p< 0.05) resulting in a significant negative correlation (r2= 0.922; p <0.05) of NET to NE content. The neurotoxin 6-hydroxydopamine, a NET substrate, reduced NE content more in the ventricles than the atria demonstrating functional significance of high ventricular NET binding. In summary, there is a ventricular predominance of NET binding that corresponds to a high NE reuptake capacity in the ventricles, yet negatively correlates to tissue NE content.
