Hyperpolarization, but not depolarization, increases intracellular Ca2+ level in cultured chick myoblasts

Jae Yong Park, Doyun Lee, Ji Ung Maeng, Kyungjin Kim, Duk Su Koh

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)


Ca2+ influx appears to be important for triggering myoblast fusion. It remains, however, unclear how Ca2+ influx rises prior to myoblast fusion. The present study examines a possible involvement of the voltage-dependent Ca2+ influx pathways. Treatment with the L-type Ca2+ channel blockers, diltiazem, and nifedipine did not alter cytosolic Ca2+ levels. Depolarization with high K+ solution and activation of Ca2+ channel with Bay K 8644, and agonist of voltage dependent Ca2+ channels, failed to elicit increases intracellular Ca2+ level, indicating the absence of depolarization-operated mechanisms. In contrast, phloretin, an agonist of Ca2+-activated potassium (KCa) channels, was able to hyperpolarize membrane potential and promoted Ca2+ influx. These effects were completely abolished by treatment of charybdotoxin, a specific inhibitor of KCa channels. In addition, gadolinium, a potent stretch-activated channel (SAC) blocker, prevented the phloretin-mediated Ca2+ increase, indicating the involvement of SACs in Ca2+ influx. Furthermore, phloretin stimulated precocious myoblast fusion and this effect was blocked with gadolinium or charybdotoxin. Taken together, these results suggest that induced hyperpolarization, but not depolarization increases Ca2+ influx through stretch-activated channels, and in turn triggers myoblast fusion.

Original languageEnglish
Pages (from-to)1176-1182
Number of pages7
JournalBiochemical and biophysical research communications
Issue number4
Publication statusPublished - 2002
Externally publishedYes

Bibliographical note

Funding Information:
This work was supported by a grant from the Korea Research Foundation. Jae-Yong Park, Doyun Lee, and Ji-Ung Maeng are supported by a Brain Korea 21 research fellowship from the Korea Ministry of Education.


  • Ca influx
  • Hyperpolarization
  • K channels
  • Myoblast fusion
  • Stretch-activated channels

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology


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