Surface-potential theory for explaining the increase in sodium permeability seen in hypocalcemia

Type of article: Letter to the editor

Anand Bhaskar, Department of Physiology, Christian Medical College, Vellore, 632002, India. E-mail: anandbhaskar [at] sify [dot] com.

Received 23 January 2008; accepted 24 January 2008.

We are aware that hypocalcemia decreases the activation threshold of sodium channels. How does this happen? It can be explained on the basis of the surface-potential theory [1]. According to this theory, the outer surface of cells has a net negative charge. When calcium levels are high, these charges get neutralized by calcium and the electric field in the membrane is purely due to the resting potential. When there is low or zero calcium, the outer surface has a net negative charge and hence, a local negative potential or surface potential is created. The voltage sensor in the sodium channel will sense this change in electric field as depolarization. This results in the opening of sodium channels and thereby an increase in excitability.

Reference:

[1] Hille B. Chapter 13. Modifiers of gating; In: Ionic channels of excitable membranes, 1st edition, Sinauer Associates Inc, Sunderland, Massachusetts, 1984.

Conflict of interests: none declared.

Please cite this letter as Bhaskar A. Surface-potential theory for explaining the increase in sodium permeability seen in hypocalcemia. Medical Physiology Online, article 3.6, volume 1, 2008, available from http://medicalphysiologyonline.blogspot.com [Link]

Reviewed by E.S.Prakash, Editor, Medical Physiology Online.