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(Hypertension. 2006;47:735.)
© 2006 American Heart Association, Inc.

Original Articles

Coexpression of Voltage-Dependent Calcium Channels Ca_v1.2, 2.1a, and 2.1b in Vascular Myocytes

Ditte Andreasen; Ulla G. Friis; Torben R. Uhrenholt; Boye L. Jensen; Ole Skøtt; Pernille B. Hansen

From the Physiology and Pharmacology, University of Southern Denmark, Odense, Denmark.

Correspondence to Pernille B. Hansen, Department of Physiology and Pharmacology, University of Southern Denmark, Winsløwparken 21, 3, DK-5000, Odense C, Denmark. E-mail pbhansen{at}health.sdu.dk

Voltage-dependent Ca²⁺ channels Ca_v1.2 (L type) and Ca_v2.1 (P/Q type) are expressed in vascular smooth muscle cells (VSMCs) and are important for the contraction of renal resistance vessels. In the present study we examined whether native renal VSMCs coexpress L-, P-, and Q-type Ca²⁺ currents. The expression of both Ca_v2.1a (P-type) and Ca_v2.1b (Q-type) mRNA was demonstrated by RT-PCR in renal preglomerular vessels from rats and mice. Immunolabeling was performed on A7r5 cells, renal cryosections, and freshly isolated renal VSMCs with anti-Ca_v1.2 and anti-Ca_v2.1 antibodies. Conventional and confocal microscopy revealed expression of both channels in all of the smooth muscle cells. Whole-cell patch clamp on single preglomerular VSMCs from mice showed L-, P-, and Q-type currents. Blockade of the L-type currents by calciseptine (20 nmol/L) inhibited 35.6±3.9% of the voltage-dependent Ca²⁺ current, and blocking P-type currents (-agatoxin IVA 10 nmol/L) led to 20.2±3.0% inhibition, whereas 300 nmol/L of agatoxin IVA (blocking P/Q-type) inhibited 45.0±7.3%. In rat aortic smooth muscle cells (A7r5), blockade of L-type channels resulted in 28.5±6.1% inhibition, simultaneous blockade of L-type and P-type channels inhibited 58.0±11.8%, and simultaneous inhibition of L-, P-, and Q-type channels led to blockade (88.7±5.6%) of the Ca²⁺ current. We conclude that aortic and renal preglomerular smooth muscle cells express L-, P-, and Q-type voltage-dependent Ca²⁺ channels in the rat and mouse.

Key Words: kidney • muscle, smooth • calcium

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