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(Hypertension. 1998;31:254.)
© 1998 American Heart Association, Inc.

Scientific Contributions

Stretch-Activated Channels in Arterial Smooth Muscle of Genetic Hypertensive Rats

Yusuke Ohya; Natsuko Adachi; Yoshito Nakamura; Motoko Setoguchi; Isao Abe; Masatoshi Fujishima

From the Second Department of Internal Medicine, Faculty of Medicine, Kyushu University, Fukuoka, Japan.

Correspondence to Yusuke Ohya, MD, Second Department of Internal Medicine, Faculty of Medicine, Kyushu University, Maidashi 3-1-1, Higashi-ku Fukuoka 812-82, Japan. E-mail ohya{at}intmed2.med.kyushu-u.ac.jp

Electrical and contractile responses of small arteries to mechanical stress are reportedly enhanced in spontaneously hypertensive rats (SHR), compared with those in Wistar Kyoto rats (WKY). We have previously shown that stretch-activated cation channels exist in arterial smooth muscle membrane, of which opening causes Na⁺ and Ca²⁺ influx and membrane depolarization. We thus hypothesize that activation of stretch-activated channels is enhanced in arterial smooth muscle of SHR compared with WKY. To test this hypothesis, stretch-activated channels is enhanced in arterial smooth muscle cells of resistance mesenteric arteries from SHR and WKY (16 to 24 weeks of age). In the whole-cell recording, membrane stretch was applied by inflating the cell with positive pressure to the recording pipette. Cell-inflation evoked Gd³⁺ -sensitive cation currents. This current appeared with less stretch stimulation and its amplitude was larger in SHR cells compared with WKY cells. In the cell-attached recording, suction to the recording pipette evoked single stretch-activated channel currents (conductance of 32 pS with 150 mmol/L Na⁺), which were blocked by Gd³⁺. Channels were activated with less negative pressure and their availability was greater in SHR cells than in WKY cells. Results suggest that the activation of stretch-activated channels is enhanced in smooth muscle of resistance arteries from SHR compared with WKY, which may contribute to the enhanced vascular responses to mechanical stress in SHR.

Key Words: electrophysiology • vascular smooth muscle • stretch • hypertension • mechanosensitive channel

Abbreviations: SHR = spontaneously hypertensive rats • WKY = Wister Kyoto rats • SA channels = stretch-activated channels • 20-HETE = 20-hydroxyeicosateteraenoic acid

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