Clemo H F, Stambler B S, Baumgarten C M
Departments of Internal Medicine, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA, USA.
Circ Res. 1999 Feb 5;84(2):157-65. doi: 10.1161/01.res.84.2.157.
The hypothesis that cellular hypertrophy in congestive heart failure (CHF) modulates mechanosensitive (ie, swelling- or stretch-activated) anion channels was tested. Digital video microscopy and amphotericin-perforated-patch voltage clamp were used to measure cell volume and ion currents in ventricular myocytes isolated from normal dogs and dogs with rapid ventricular pacing-induced CHF. In normal myocytes, osmotic swelling in 0.9T to 0.6T solution (T, relative osmolarity; isosmotic solution, 296 mOsmol/L) was required to elicit ICl,swell, an outwardly rectifying swelling-activated Cl- current that reversed near -33 mV and was inhibited by 1 mmol/L 9-anthracene carboxylic acid (9AC), an anion channel blocker. Block of ICl,swell by 9AC simultaneously increased the volume of normal cells in hyposmotic solutions by up to 7%, but 9AC had no effect on volume in isosmotic or hyperosmotic solutions. In contrast, ICl,swell was persistently activated under isosmotic conditions in CHF myocytes, and 9AC increased cell volume by 9%. Osmotic shrinkage in 1.1T to 1.5T solution inhibited both ICl,swell and 9AC-induced cell swelling in CHF cells, whereas osmotic swelling only slightly increased ICl,swell. The current density for fully activated 9AC-sensitive ICl,swell was 40% greater in CHF than normal myocytes. In both groups, 9AC-sensitive current and 9AC-induced cell swelling were proportional with changes in osmolarity and 9AC concentration, and the effects of 9AC on current and volume were blocked by replacing bath Cl- with methanesulfonate. CHF thus altered the set point and magnitude of ICl,swell and resulted in its persistent activation. We previously observed analogous regulation of mechanosensitive cation channels in the same CHF model. Mechanosensitive anion and cation channels may contribute to the electrophysiological and contractile derangements in CHF and may be novel targets for therapy.
本研究对充血性心力衰竭（CHF）时细胞肥大调节机械敏感（即肿胀或牵张激活）阴离子通道这一假说进行了验证。采用数字视频显微镜和两性霉素穿孔膜片钳技术，测量从正常犬和快速心室起搏诱导CHF的犬分离出的心室肌细胞的细胞体积和离子电流。在正常心肌细胞中，需将细胞置于0.9T至0.6T溶液（T，相对渗透压；等渗溶液为296 mOsmol/L）中进行渗透性肿胀，才能诱发ICl,swell，即一种外向整流的肿胀激活Cl-电流，其反转电位接近-33 mV，并被1 mmol/L 9-蒽甲酸（9AC）（一种阴离子通道阻滞剂）抑制。9AC阻断ICl,swell的同时，可使低渗溶液中正常细胞的体积增加高达7%，但9AC对等渗或高渗溶液中的细胞体积无影响。相比之下，在CHF心肌细胞的等渗条件下，ICl,swell持续激活，9AC可使细胞体积增加9%。在1.1T至1.5T溶液中进行渗透性收缩可抑制CHF细胞中的ICl,swell和9AC诱导的细胞肿胀，而渗透性肿胀仅使ICl,swell略有增加。CHF时完全激活的9AC敏感的ICl,swell的电流密度比正常心肌细胞大40%。在两组中，9AC敏感电流和9AC诱导的细胞肿胀均与渗透压和9AC浓度的变化成比例，用甲磺酸盐替代浴液中的Cl-可阻断9AC对电流和体积的影响。因此，CHF改变了ICl,swell的设定点和幅度，并导致其持续激活。我们之前在同一CHF模型中观察到机械敏感阳离子通道的类似调节。机械敏感阴离子和阳离子通道可能导致CHF中的电生理和收缩紊乱，可能是新的治疗靶点。
