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

在连续喂养含有正常生长所需的最低钠的饮食中的Wistar大鼠，与正常钠饮食的大鼠相比，血压较低，交感神经功能受到抑制。然而，在同样的低钠饮食中饲养的SHR长大后会患上高血压。为了阐明为什么饮食钠限制对预防SHR患者高血压没有效果，我们研究了钠消耗对与肾小管钠重吸收有关的α -肾上腺素能受体的影响。Wistar Kyoto大鼠（WKY）和SHR分别饲喂低钠（0.05%）和正常钠（0.4%）日粮。6、8、20周龄测量血压、体重和24小时尿钠排泄量1 d后，取肾，用Percall制备肾近端小管基底外膜。肾上腺素能受体的测定通过使用[^3H]-prazosin， α -1拮抗剂和[^3H]- rauwolsciine， α -2拮抗剂完成。低钠饮食组的体重增长和血压与正常饮食组相似。α -1受体的最大结合（Bmax）在任何年龄正常和低钠组之间没有差异。解离常数（Kd）在8周龄时增加，两组间无差异。两组间α -2受体的Bmax和Kd值相近。在SHR中，低钠组和正常钠组的身体生长和血压没有差异。8周龄时血压升高至高血压水平。低钠状态下SHR患者24小时尿钠排泄量低于预期。SHR中α -1受体的Bmax和Kd在任何年龄正常组和低na组之间均无显著差异。低钠组8周龄时α -2受体Bmax显著升高，正常钠组8周龄时α -2受体Bmax略有升高，但随年龄增长Bmax显著升高。低钠组8周龄Bmax高于正常钠组SHR组和低钠组WKY组。α -2受体的Kd值在两组小鼠周内各年龄均相似。结果表明，即使在钠限制的情况下，SHR也可以增加肾小管中的α -2受体，这可能加速钠的重吸收并产生高血压。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