Inhibition of calcium influx and tonic response to K+ of intestinal smooth muscle by hydralazine.

Journal of autonomic pharmacology Pub Date : 1996-06-01
T Nasu, S Yanagimoto
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Abstract

1. Evidence concerning the mechanism of the inhibition of contraction caused by hydralazine has been sought in ileal longitudinal muscle and taenia coli of guinea-pig. Hydralazine (10(-3)-3 x 10(-3) M) markedly inhibited K+ (60 mM) induced tonic response with smaller effects on the phasic response in the ileal muscle. However, 10(-2) M hydralazine completely abolished both responses. 2. Hydralazine increased the threshold for Ca2+ induced contraction in Ca2+ free, K+ depolarized taenia coli and reduced the maximal response size. A low concentration (3 x 10(-10) M) of nifedipine, an L-type Ca2+ channel blocker, further caused a parallel shift to the right in the presence of hydralazine in the concentration-response curves obtained with Ca2+ 3. Hydralazine caused a significant decrease in Ca2+ uptake measured by the lanthanum method during the K+ induced tonic response in ileal muscle; however, it did not affect the Ca2+ efflux. 4. In ileal muscle fibres treated with Triton-X-100, in which the Ca2+ release sites are destroyed, 10(-3) M hydralazine had no effect on the contractions induced by 10(-5) M Ca2+; however, hydralazine at a higher concentration (10(-2) M) had a slight inhibitory effect on the contraction. 5. The present finding indicates that the inhibitory action on contractions produced by hydralazine may result mainly from the interference of calcium permeability at the cell membrane in ileal muscle. There is the possibility that hydralazine of higher concentrations may have a minor action on the contractile system.

肼嗪抑制肠平滑肌钙内流及对K+的强直反应。
1. 本文在豚鼠回肠纵肌和大肠带绦虫中探讨了肼嗪抑制收缩的机制。海氮嗪(10(-3)-3 × 10(-3) M)显著抑制K+ (60 mM)诱导的紧张性反应,对回肠肌相反应的影响较小。然而,10(-2)M肼嗪完全消除了这两种反应。2. Hydralazine提高了Ca2+诱导的无Ca2+、K+去极化大肠带绦虫的收缩阈值,降低了最大反应大小。低浓度(3 × 10(-10) M)的硝苯地平,一种l型Ca2+通道阻滞剂,进一步引起平行向右移动在存在肼嗪的浓度-响应曲线与Ca2+ 3。在钾离子诱导的强直反应中,海达拉嗪引起回肠肌钙离子摄取的显著降低;然而,它不影响Ca2+外排。4. 用Triton-X-100处理回肠肌纤维,Ca2+释放位点被破坏,10(-3)M肼嗪对10(-5)M Ca2+诱导的收缩没有影响;而较高浓度(10(-2)M)的肼嗪对收缩有轻微的抑制作用。5. 本研究结果表明,肼嗪对回肠收缩的抑制作用可能主要是由于对回肠肌细胞膜钙通透性的干扰。高浓度的肼嗪可能对收缩系统有轻微的作用。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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