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

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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.
Original languageEnglish
JournalCanadian Journal of Physiology and Pharmacology
Volume87
Issue number1
Pages (from-to)8-20
Number of pages12
ISSN0008-4212
DOIs
Publication statusPublished - 2009

Bibliographical note

Keywords: Animals; Arterioles; Calcium; Calcium Channels, T-Type; Endothelium, Vascular; Humans; Mesenteric Arteries; Muscle, Smooth, Vascular; Vasoconstriction

ID: 18763670