The influence of low Na diet on the sympathetic nervous system and the alpha-receptor of renal basolateral membrane in spontaneously hypertensive rat.

在连续饲养的Wistar大鼠中，与正常钠饮食相比，连续饲养的Wistar大鼠的血压较低，交感神经功能受到抑制。然而，在相同的缺钠饮食下长大的自发性高血压患者会患上高血压。为了阐明饮食限钠对预防SHR高血压没有作用的原因，我们研究了钠缺乏对与肾小管钠重吸收有关的α-肾上腺素能受体的影响。分别于6、8、20周龄测定血压、体重和24小时尿钠排泄量后1d，取肾，用Percall制备肾近端小管基外侧膜。肾上腺素能受体的测定是通过使用α-1拮抗剂[^~3H]-哌唑嗪和α-2拮抗剂[^~3H]-rauwolscine来完成的。B…低钠饮食WKY大鼠的生长发育和血压水平与正常钠饮食相似。在任何年龄段，正常钠组和低钠组的α-1受体最大结合量(Bmax)没有差异。离解常数(Kd)在8周龄时升高，两组间差异无统计学意义。在WKY中，两组α2受体的Bmax和Kd相似。在SHR中，低钠组和正常钠组在体格生长和血压方面没有差异。血压在8周龄时升至高血压水平。低钠组SHR 24小时尿钠排泄量低于预期。各年龄段SHRα1受体Bmax和Kd在正常钠组和低钠组之间均无显著差异。低钠组SHRα2受体Bmax在8周龄时显著增加，而正常钠组随增龄略有增加，但差异显著。8周龄低钠组Bmax高于正常钠组和WKY组。α-2受体的Kd在所有周龄两组间相似。结果提示，即使在钠限制下，SHR仍可增加肾小管上皮细胞的α-2受体，这可能加速了钠的重吸收，从而导致高血压的发生。较少

In Wistar rats bred successively on a diet containing the minimum sodium required for normal growth, blood pressure was lower and sympathetic nervous function was suppressed compared to those on normal sodium diet. However, SHR bred on the same sodium depleted diet grew up to hypertensive. To clarify why dietary sodium restriction has no effect to prevent hypertension in SHR, we studied an influence of sodium depletion on alpha-adrnergic receptors which were concerned with reabsorption of sodium in the renal tubules.Wistar Kyoto rat (WKY) and SHR were fed with a diet containing low Na (0.05%) or normal Na (0.4%). One day after the measurements of blood pressure, body weight and 24 hour urinary Na output at the age of 6, 8, 20 weeks, the kidneys were removed and the basolateral membranes of renal proximal tubules were preparated using Percall. Assay of adrenergic receptors was accomplished through the use of [^3H]-prazosin, alpha-1 antagonist, and [^3H]-rauwolscine, alpha-2 antagonist.B … More ody growth and blood pressure in WKY on low Na diet were similar to those on normal Na diet. Maximum binding (Bmax) for alpha-1 receptors was not different between the normal-and low-Na group at any age. Dissociation constants (Kd) increased at 8 weeks of age with no difference between the both groups. Bmax and Kd for alpha-2 receptor was similar between two groups in WKY.There was no difference in body growth and blood pressure between the low- and normal-Na group in SHR. Blood pressure increased to a hypertensive level at the age of 8 weeks. Urinary sodium excretion for 24 hours was less in SHR on low-Na than the expected. There was no significant difference in both Bmax and Kd for alpha-1 receptor between the normal-and low-Na group in SHR at any age. Bmax for the alpha-2 receptor increased markedly at 8 weeks of age in SHR on low-Na, while it increased slightly but significantly with aging in SHR on normal-Na diet. Bmax at 8 weeks of age on low-Na was higher than that in SHR on normal-Na diet or WKY on low-Na. Kd for alpha-2 receptor was similar between the 2 groups at all age of the week. The results suggest that SHR has access to increase alpha-2 receptors in the renal tubules even under sodium restriction, which might accelerate Na reabsorption and produce hypertension. Less