Protein kinase inhibitor H-89 reverses forskolin stimulation of cardiac L- type calcium current

W. Yuan, Donald M Bers

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


Calcium currents (I(Ca)) and barium currents (I(Ba)) were measured in freshly isolated single ferret ventricular myocytes, using the whole cell patch-clamp and perforated patch-clamp techniques with Na and K currents blocked by tetraethylammonium and Cs. The membrane potential (E(m)) dependence of activation and steady-state inactivation curves were determined using a Boltzmann relation, where E0.5 is the E(m) at half-maximal conductance. Forskolin (1 μM) increased the rate of I(Ca) inactivation, especially in perforated patch, but slowed I(Ba) inactivation. The acceleration is likely to be due to greater Ca-dependent inactivation of I(Ca), where the slowing of I(Ba) inactivation may be due to protein kinase A-dependent slowing of E(m)-dependent inactivation. Forskolin (1-10 μM) also increased I(Ca) amplitude by two- to threefold and shifted the E0.5 for both activation and inactivation to more negative potentials by 7-8 mV. The effect of forskolin on the amplitude of I(Ca) could be reversed by an inhibitor of adenosine 3',5'-cyclic monophosphate-dependent protein kinase, N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide (H-89; 1-10 μM). However, H-89 did not reverse the shift of E0.5 induced by forskolin. H- 89 application by itself does not decrease basal I(Ca) but does shift the E0.5 of both activation and inactivation to more negative values of E(m). It is possible that H-89 reverses the shift induced by regulatory phosphorylation (due to forskolin) but induces a coincidental negative shift itself.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Cell Physiology
Issue number3 37-3
StatePublished - 1995
Externally publishedYes


  • adenosine 3',5'-cyclic monophosphate- dependent protein kinase
  • calcium current
  • cardiac myocytes
  • N-[2-(p-bromocinnamylamino)ethyl]-5- isoquinolinesulfonamide

ASJC Scopus subject areas

  • Cell Biology
  • Clinical Biochemistry
  • Physiology
  • Agricultural and Biological Sciences(all)


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