Electrophysiological properties of neonatal rat ventricular myocytes with alpha1-adrenergic-induced hypertrophy

Am J Physiol. 1998 Aug;275(2):H577-90. doi: 10.1152/ajpheart.1998.275.2.H577.


The electrophysiology of neonatal rat ventricular myocytes with and without hypertrophy has not been characterized. The alpha1-adrenergic agonist phenylephrine induced hypertrophy in neonatal rat ventricular myocytes. After 48 h of exposure to 20 microM phenylephrine, cell surface area of hypertrophied myocytes was 44% larger than control. Action potential duration was significantly longer in hypertrophy than in control. There was an increase in L-type Ca2+ current in control after 48 h in culture, but current density was significantly less in hypertrophy (-4.7 +/- 0.8 hypertrophy vs. -10.7 +/- 1.2 control pA/pF, n = 22, P < 0.05). T-type Ca2+ current density was not different. The alpha-adrenergic antagonist prazosin blocked the hypertrophy and the chronic effect of phenylephrine on L-type Ca2+ current. Transient outward K+ current density was decreased 70% in hypertrophy and was blocked with 4-aminopyridine. No change in Na+ current density was observed. Staurosporine, a protein kinase C inhibitor, eliminated the hypertrophy and the effect on L-type Ca2+ current. These studies showed that phenylephrine-induced hypertrophy occurred via the alpha1-adrenergic pathway and caused electrophysiological changes and effects on ion channel expression.

MeSH terms

  • Action Potentials / drug effects
  • Adrenergic alpha-1 Receptor Agonists
  • Analysis of Variance
  • Animals
  • Animals, Newborn
  • Barium / metabolism
  • Calcium Channels / drug effects
  • Calcium Channels / physiology
  • Calcium Channels, L-Type
  • Cardiomegaly / physiopathology*
  • Cells, Cultured
  • Heart / drug effects*
  • Heart / physiology
  • Heart / physiopathology
  • Heart Ventricles
  • Myocardium / cytology
  • Patch-Clamp Techniques
  • Phenylephrine / pharmacology*
  • Prazosin / pharmacology
  • Propranolol / pharmacology
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Adrenergic, alpha-1 / physiology*
  • Sodium Channels / physiology


  • Adrenergic alpha-1 Receptor Agonists
  • Calcium Channels
  • Calcium Channels, L-Type
  • Receptors, Adrenergic, alpha-1
  • Sodium Channels
  • Phenylephrine
  • Barium
  • Propranolol
  • Prazosin