The role of sarcoplasmic reticulum in small resistant artery in hypertension

为了研究自发性高血压大鼠（SHR）小阻力动脉中钙（Ca）的固存在高血压发展中的作用，我们用ryanodine （Ry: SR Ca释放通道打开剂）和thapsigarin （Tg: SR Ca- atpase抑制剂）测量了高钾诱导的SHR肌浆网（SR） Ca储存消耗前后SHR的系膜上动脉收缩。在5周龄（幼龄）和10周龄（成年）SHR和年龄匹配的Wistar-Kyoto大鼠（WKY）中，测量了肠系膜上动脉第一或第二分支环的等长张力。在暴露于10muM Ry或1muM Tg之前和之后，测量了施用40mM钾5分钟诱导的反应。成人SHR患者的收缩压明显高于其他组。钾诱导的收缩幅度在两种幼株中几乎相同，但在成年株中SHR明显大于WKY。暴露于Ry或Tg后，青壮年和成年WKY的More e幅度较对照略有增加，而青壮年和成年SHR的More e幅度则明显增加。此外，暴露于Ry或Tg后，成年SHR的强度明显大于年轻SHR。幼株和成株在洗钾后的松弛速率基本相同。在幼年期和成年期，与幼年期相比，暴露于Ry或Tg后的SHR速率都大大延迟，而且在成年期SHR中达到最大松弛50%以上所需的时间也比幼年期SHR明显延迟。这些结果表明，SHR中SR对Ca的吸收大于WKY，并且SHR中SR的细胞外内流和Ca泵活性均呈年龄依赖性增加。综上所述，SR中的Ca泵通过对胞浆游离Ca. Less升高的缓冲作用，在SHR高血压的发生和发展中起重要作用

To study the role of calcium (Ca) sequestration by SR in small resistance artery to progression of hypertension in spontaneously hypertensive rats (SHR), we measured high-potassium-induced contraction in the superior mesenteric artery in SHR befor and after depleting sarcoplasmic reticulum (SR) Ca stores using ryanodine (Ry : SR Ca release channel opener) and thapsigargin (Tg : SR Ca-ATPase inhibitor). Isometric tension was measured in the rings of the first or second branch of the superior mesenteric artery in both 5-week-old (young) and 10-week-old (adult) SHR,and age matched Wistar-Kyoto rats (WKY).Responses induced by application of 40mM potassium for 5 minutes were measured before and after exposure to 10muM Ry or 1muM Tg. Systolic blood pressure was significantly higher in adult SHR than in the other groups. The magnitude of potassium-induced contraction was almost the same in both young strains, but significantly larger in SHR than in WKY in adult. After exposure to Ry or Tg, th … More e magnitude was slightly increased compared with the control contraction in young and adult WKY,but greatly increased in young and adult SHR.Moreover, the magnitude, after exposure to Ry or Tg, was significantly larger in adult SHR than in young SHR.The rate of relaxation after washout of potassium was almost the same in both young strains and adult strains, respectively. The rate after exposure to Ry or Tg was greatly delayd in SHR compared in WKY in both young and adult phases, and moreover, the time taken to reach over 50% of maximum relaxation after the agents was significantly delayd in adult SHR compared with young SHR.These results suggest that Ca sequestration by the SR in SHR was greater than in WKY,and both Ca influx from extracellular space and the Ca pump activity of SR in SHR increased age-dependently. Therefore, it is concluded that Ca pump in SR plays an important role in preventing the development and progression of hypertension in SHR via a buffering effect on the elevation of cytosolic free Ca. Less