title: Protective role of acidic pH-activated chloride channel in severe acidosis-induced contraction from the aorta of spontaneously hypertensive rats.
abstract: Severe acidic pH-activated chloride channel (ICl,acid) has been found in various mammalian cells. In the present study, we investigate whether this channel participates in reactions of the thoracic aorta to severe acidosis and whether it plays a role in hypertension. We measured isometric contraction in thoracic aorta rings from spontaneously hypertensive rats (SHRs) and normotensive Wistar rats. Severe acidosis induced contractions of both endothelium-intact and -denuded thoracic aorta rings. In Wistar rats, contractions did not differ at pH 6.4, 5.4 and 4.4. However, in SHRs, contractions were higher at pH 5.4 or 4.4 than pH 6.4, with no difference between contractions at pH 5.4 and 4.4. Nifedipine, ICl,acid blockers 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) and 4,4'-diisothiocyanatostilbene-2, 2'-disulfonic acid (DIDS) inhibited severe acidosis-induced contraction of aortas at different pH levels. When blocking ICl,acid, the remnant contraction was greater at pH 4.4 than pH 5.4 and 6.4 for both SHRs and Wistar rats. With nifedipine, the remnant contraction was greatly reduced at pH 4.4 as compared with at pH 6.4 and 5.4. With NPPB or DIDS, the ratio of remnant contractions at pH 4.4 and 5.4 (R4.4/5.4) was lower for SHRs than Wistar rats (all <1). However, with nifedipine, the R4.4/5.4 was higher for SHRs than Wistar rats (both >1). Furthermore, patch clamp recordings of ICl,acid and intracellular Ca(2+) measurements in smooth muscle cells confirmed these findings. ICl,acid may protect arteries against excess vasoconstriction under extremely acidic extracellular conditions. This protective effect may be decreased in hypertension.
authors.affiliation: Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education and Chinese Ministry of Public Health, Department of Cardiology, Qilu Hospital, Shandong University, Jinan, China.
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Ma
authors.forename: Jia
authors.initials: J
authors.lastname: Qi
authors.forename: Zhijie
authors.initials: Z
authors.lastname: Fu
authors.forename: Mingying
authors.initials: M
authors.lastname: Ling
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.forename: Yun
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000138:Acidosis / Q000378:metabolism*; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006973:Hypertension / Q000378:metabolism*; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism; D009579:Nitrobenzoates / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR
chemical_list: D018118:Chloride Channels; D009579:Nitrobenzoates; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D002118:Calcium