Xiao Y F, McArdle J J
Department of Pharmacology and Toxicology, New Jersey Medical School (UMDNJ), Newark 07103-2714.
J Hypertens. 1994 Jul;12(7):783-90.
The membrane current mediated by the L-type calcium channel (ICa) was studied for myocytes isolated from the ventricle of 10- to 11-week-old spontaneously hypertensive rats (SHR).
Compared with age-matched normotensive Wistar-Kyoto (WKY) or Sprague-Dawley rats, the amplitude of ICa was greater for the SHR. Two observations suggest that the greater ICa of the SHR was not due to hypertrophy. First, the similarity of membrane capacitance for these three strains of rat indicated lack of hypertrophy. Secondly, the amplitude of ICa was also greater for myocytes isolated from the right ventricle of the SHR. The ICa of the SHR was more sensitive to drugs known to activate calcium channels via phosphorylation. Specifically, extracellular application of 1 mumol/l isoprenaline as well as intracellular dialysis with either 1 mmol/l cyclic AMP or with 1 mmol/l adenosine 5'-O-3-thiotriphosphate increased the mean ICa of SHR myocytes significantly more than that of WKY rat cells. The ICa of SHR myocytes was also more sensitive to BAY K 8644 and its enantiomorphs.
The present data suggest that the greater peak amplitude of ICa for SHR myocytes relative to that of myocytes of normotensive rats is due to an increase in current density and enhancement of channel phosphorylation.
对从10至11周龄自发性高血压大鼠（SHR）心室分离的心肌细胞的L型钙通道介导的膜电流（ICa）进行了研究。
与年龄匹配的正常血压Wistar-Kyoto（WKY）或Sprague-Dawley大鼠相比，SHR的ICa幅度更大。两项观察结果表明，SHR的ICa增加并非由于肥大。首先，这三种大鼠品系的膜电容相似，表明不存在肥大。其次，从SHR右心室分离的心肌细胞的ICa幅度也更大。SHR的ICa对已知通过磷酸化激活钙通道的药物更敏感。具体而言，细胞外施加1 μmol/l异丙肾上腺素以及用1 mmol/l环磷酸腺苷或1 mmol/l腺苷5'-O-3-硫代三磷酸进行细胞内透析，使SHR心肌细胞的平均ICa增加幅度明显大于WKY大鼠细胞。SHR心肌细胞的ICa对BAY K 8644及其对映体也更敏感。
目前的数据表明，SHR心肌细胞的ICa峰值幅度相对于正常血压大鼠心肌细胞更大，是由于电流密度增加和通道磷酸化增强所致。
