Circulation Research Online Only
July 9, 1999
This new era for Circulation Research is filled with innumerable opportunities for growth in the dynamic environment of Web publishing. The field of cardiovascular research is constantly evolving, and Circulation Research intends to make creative use of the new technology. Thus, we are pleased to announce the launch of online-only UltraRapid Communications as electronic pages in Circulation Research Online. This new category of UltraRapid Communications is designed specifically for the expeditious publication of cutting-edge research.
To denote which articles are published online only, a blue star appears next to the title of the article on the cover, under the heading of Circulation Research Electronic Pages. Further, this blue-bordered page displays the full abstract in the print issue; the full-length article can be accessed at www. circresaha.org. UltraRapid Communications can be cited in the same way as other articles that appear in the printed journal and will be tracked in Index Medicus, MEDLINE, PubMed, and other indexing services. This article and all future online-only articles will be denoted on the Table of Contents as e-pages.
Distribution and Prevalence of Hyperpolarization-Activated Cation Channel (HCN) mRNA Expression in Cardiac Tissues
Wenmei Shi, Randy Wymore, Hangang Yu, Jiying Wu, Rigel T. Wymore, Zongming Pan, Richard B. Robinson, Jane E. Dixon, David McKinnon, Ira S. Cohen
Abstract—HCN cation channel mRNA expression was determined in the rabbit heart and neonatal and adult rat ventricle using RNase protection assays. In the rabbit SA node, the dominant HCN transcript is HCN4, representing >81% of the total HCN message. HCN1 is also expressed, representing >18% of the total HCN mRNA. Rabbit Purkinje fibers contained almost equal amounts of HCN1 and HCN4 transcripts with low levels of HCN2, whereas rabbit ventricle contained predominantly HCN2. The SA node contained 25 times the total HCN message of Purkinje fibers and 140 times the total HCN message of ventricle. No reports of hyperpolarization-activated current (If) exist in rabbit Purkinje fibers, and we could not record If in rabbit ventricular myocytes. To investigate the possible role of isoform switching in determining the voltage dependence of If, we determined the prevalence of HCN isoforms in neonatal and adult rat ventricle. We had previously determined the threshold for activation of If to be ≈−70 mV in neonatal rat ventricle and −113 mV in adult rat ventricle. In both neonatal and adult rat ventricle, only HCN2 and HCN4 transcripts are present. The ratio of HCN2 to HCN4 is ≈5:1 in the neonate and 13:1 in the adult. Taken together, these results suggest that different cardiac regions express different isoforms of the HCN family. The HCN1 and HCN4 isoforms are most closely associated with a depolarized threshold for If activation, whereas the HCN2 isoform is associated with a more negative activation curve. The full text of this article is available at http://www.circresaha.org. (Circ Res. 1999;85:e1-e6.)
Key Words: RNase protection assay▪mRNA distribution▪hyperpolarization-activated current
Web Site Feature
The full-length article can be found on the World Wide Web at http://www.circresaha.org
- © 1999 American Heart Association, Inc.