Volume 12, No 5-6, Dec 2002

ISSN: 1001-0602 
EISSN: 1748-7838 2018 
impact factor 17.848* 
(Clarivate Analytics, 2019)

Volume 12 Issue 5-6, December 2002: 385-394

ORIGINAL ARTICLES

Developmental changes in functional expression and β-adrenergic regulation of I_f in the heart of mouse embryo

Gui Li SONG¹, Ming TANG^1,*, Chang Jin LIU¹, Hong Yan LUO¹, Hua Min LIANG¹, Xin Wu HU¹, JiaoYa XI¹, Lin Lin GAO¹, Bernd FLEISCHMANN², Jürgen HESCHELER²

¹Department of Physiology, Tongji Medical College of Huazhong University of Science and Technology, Wuhan 430030, China

²Institute of Neurophysiology, University of Cologne, D-50931 Cologne, Germany Correspondence: Ming TANG(tangming49@hotmail.com )

The hyperpolarization-activated current (I_f) plays an important role in determining the spontaneous rate of cardiac pacemaker cells. The automatic rhythmicity also exists in working cells of embryonic heart, therefore we studied developmental changes in functional expression and b-adrenergic regulation of I_f in embryonic mouse heart. The expression of I_f is high in early developmental stage (EDS) (10.5 d after coitus) ventricular myocytes, low in intermediate developmental stage (IDS) (13.5 d) atrial or ventricular myocytes and even lower in late developmental stage (LDS) (16.5 d) atrial or ventricular myocytes, indicating that these cells of the EDS embryonic heart have some properties of pacemaker cells. b-adrenergic agonist isoproterenol (ISO) stimulates I_f in LDS but not in EDS cardiomyocytes, indicating that the b-adrenergic regulation of I_f is not mature in EDS embryonic heart. But forskolin (a direct activator of adenylate cyclase) and 8-Br-cAMP (a membrane-permeable analogue of cAMP) increase the amplitude of I_f in EDS cells, indicating that adenylate cyclase and cAMP function fairly well at early stage of development. Furthermore, the results demonstrate that I_f is modulated by phosphorylation via cAMP dependent PKA both in EDS and LDS cells.

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