In:
Canadian Journal of Physiology and Pharmacology, Canadian Science Publishing, Vol. 87, No. 1 ( 2009-01), p. 8-20
Abstract:
The largest peripheral blood pressure drop occurs in terminal arterioles ( 〈 40 µm lumen diameter). L-type voltage-dependent Ca 2+ channels (VDCCs) are considered the primary pathway for Ca 2+ 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 Ca 2+ for contraction of VSMC has been disputed. However, T-type channels display non-inactivating window currents, which may play a role in sustained Ca 2+ entry. Here, we review the possible role of T-type channels in vasomotor tone regulation in rat mesenteric terminal arterioles. The Ca V 3.1 channel was immunolocalized in VSMC, whereas the Ca V 3.2 channel was predominantly expressed in endothelial cells. Voltage-dependent Ca 2+ 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.
Type of Medium:
Online Resource
ISSN:
0008-4212
,
1205-7541
Language:
English
Publisher:
Canadian Science Publishing
Publication Date:
2009
detail.hit.zdb_id:
2004356-9
