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(Hypertension. 1999;34:39-43.)
© 1999 American Heart Association, Inc.

Scientific Contributions

Endothelium-Derived Contracting Factor in Carotid Artery of Hypertensive Dahl Rats

Ming-Sheng Zhou; Yasuhiro Nishida; Qing-Hui Chen; Hiroaki Kosaka

From the Second Department of Physiology, Kagawa Medical University (Japan).

Correspondence to Hiroaki Kosaka, MD, PhD, Second Department of Physiology, Kagawa Medical School, 1750-1, Ikenobe, Miki-cho, Kita, Kagawa 761-0793, Japan. E-mail hkosaka{at}kms.ac.jp

Abstract—The present study is designed to investigate whether acetylcholine (ACh) elicits an endothelium-derived contracting factor (EDCF) and whether it contributes to decreased relaxant response induced by ACh in Dahl rats. Dahl salt-sensitive (DS) and -resistant (DR) rats were fed a 0.4% NaCl or an 8% NaCl diet for 4 weeks. High sodium intake significantly increased blood pressure in DS rats but not in DR rats. The carotid rings were suspended for isometric tension recording. ACh caused an endothelium-dependent contraction in carotid rings from hypertensive DS rats but not from normotensive Dahl rats. Atropine, indomethacin, SQ29548, or ONO-3708 (prostaglandin H₂ [PGH₂]/thromboxane A₂ [TXA₂] receptor antagonist) abolished ACh-induced contraction, and OKY-046 (inhibitor of TXA₂ synthetase) partially attenuated the contraction. High sodium intake significantly enhanced contraction evoked by U46619, a PGH₂/TXA₂ receptor agonist, in both DS and DR rats. In contrast, ACh-induced relaxation was significantly depressed in the rings from hypertensive DS rats, and ONO-3708 partially improved the depressed relaxation. Administration of ONO-8809 (an orally active PGH₂/TXA₂ receptor antagonist; 30 µg per body per day) for 4 weeks neither reduced blood pressure nor improved the depressed ACh-induced relaxation in hypertensive DS rats. These results suggest that ACh causes release of EDCF in carotid rings of hypertensive DS rats, which is likely to be PGH₂ and TXA₂. The EDCF contributed in part to the depressed ACh-induced relaxation.

Key Words: acetylcholine • arteries • rats, Dahl • endothelium-derived relaxing factor • hypertension, sodium dependent • receptors • prostaglandin • thromboxane

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