Is there a role for T-type Ca2+ channels in regulation of vasomotor tone in mesenteric arterioles?

Can J Physiol Pharmacol. 2009 Jan;87(1):8-20. doi: 10.1139/Y08-101.

Abstract

The largest peripheral blood pressure drop occurs in terminal arterioles (<40 microm lumen diameter). L-type voltage-dependent Ca2+ channels (VDCCs) are considered the primary pathway for Ca2+ influx during physiologic activation of vascular smooth muscle cells (VSMC). Recent evidence suggests that T-type VDCCs are expressed in renal afferent and efferent arterioles, mesenteric arterioles, and skeletal muscle arterioles. T-type channels are small-conductance, low voltage-activated, fast-inactivating channels. Thus, their role in supplying Ca2+ for contraction of VSMC has been disputed. However, T-type channels display non-inactivating window currents, which may play a role in sustained Ca2+ entry. Here, we review the possible role of T-type channels in vasomotor tone regulation in rat mesenteric terminal arterioles. The CaV3.1 channel was immunolocalized in VSMC, whereas the CaV3.2 channel was predominantly expressed in endothelial cells. Voltage-dependent Ca2+ entry was inhibited by the new specific T-type blockers R(-)-efonidipine and NNC 55-0396. The effect of NNC 55-0396 persisted in depolarized arterioles, suggesting an unusually high activation threshold of mesenteric T-type channels. T-type channels were not necessary for conduction of vasoconstriction, but appear to be important for local electromechanical coupling in VSMC. The first direct demonstration of endothelial T-type channels warrants new investigations of their role in vascular biology.

Publication types

  • Review

MeSH terms

  • Animals
  • Arterioles / physiology*
  • Calcium / metabolism
  • Calcium Channels, T-Type / physiology*
  • Endothelium, Vascular / physiology
  • Humans
  • Mesenteric Arteries / physiology*
  • Muscle, Smooth, Vascular / physiology
  • Vasoconstriction

Substances

  • Calcium Channels, T-Type
  • Calcium