Mironneau J, Savineau J P, Mironneau C
J Cardiovasc Pharmacol. 1984 Nov-Dec;6(6):1177-83.
The membrane potential and ionic currents of smooth muscle strips of the portal vein were studied in normotensive rats (WKY) and spontaneously hypertensive rats (SHR) by the double sucrose gap. The parameters of the membrane, i.e., resting potential, action potential, and maximal amplitudes of Ca and K currents were similar in WKY and SHR preparations. The maximal rate of rise of isometric contractions was increased in SHR as compared to WKY rats. The smooth muscle membrane of SHR rats was also more sensitive to noradrenaline, i.e., depolarization of the membrane appeared with 5 X 10(-9) M noradrenaline in SHR, but with 5 X 10(-8) M in WKY rats. Depolarization block of all-or-nothing action potential generation appeared at a lower concentration of noradrenaline in SHR preparations. Sensitivity of the smooth muscle membrane to angiotensin II and prostaglandin E1 was also higher in SHR as compared to WKY rats. Tienilic acid (TA, 5 X 10(-5) M) depressed both action potential and contraction amplitudes in both WKY and SHR preparations. The inward Ca current was reduced, but the K current was not. Chronic administration of TA to SHR (6 months) suppressed the increased sensitivity to noradrenaline, angiotensin II, and prostaglandin E1. The results suggest that TA acts primarily on the plasma surface of vascular smooth muscle by reducing the inward Ca current, and may, in this way, decrease both cytoplasmic Ca concentration and vascular contractility in SHR.
采用双蔗糖间隙法研究了正常血压大鼠（WKY）和自发性高血压大鼠（SHR）门静脉平滑肌条的膜电位和离子电流。WKY和SHR标本的膜参数，即静息电位、动作电位以及钙电流和钾电流的最大幅值相似。与WKY大鼠相比，SHR等长收缩的最大上升速率增加。SHR大鼠的平滑肌膜对去甲肾上腺素也更敏感，即SHR中5×10（-9）M的去甲肾上腺素可使膜去极化，而WKY大鼠中则需5×10（-8）M。在SHR标本中，去甲肾上腺素浓度较低时即可出现全或无动作电位产生的去极化阻滞。与WKY大鼠相比，SHR中平滑肌膜对血管紧张素II和前列腺素E1的敏感性也更高。替尼酸（TA，5×10（-5）M）可降低WKY和SHR标本的动作电位和收缩幅值。内向钙电流减小，但钾电流未受影响。对SHR长期给予TA（6个月）可抑制其对去甲肾上腺素、血管紧张素II和前列腺素E1敏感性的增加。结果表明，TA主要通过减少内向钙电流作用于血管平滑肌的质膜表面，从而可能降低SHR的细胞质钙浓度和血管收缩性。
