大鼠AV3V注射血管紧张素Ⅱ对近球小管Na^+,K^+-ATP酶活性的影响

Effect of AV3V microinjection of Ang Ⅱ on Na^+ ,K^+ -ATPase activity of proximal tubule in rats

目的探讨大鼠第三脑室前腹侧区(AV3V)肾素-血管紧张素系统(RAS)对近球小管Na+,K+-AT- Pase活性的影响及作用途径。方法用小动物脑立体定位仪在大鼠AV3V埋植钢管供中枢注射,放射免疫法测定血浆血管紧张素Ⅱ(AngⅡ)及血清内源性洋地黄样物质(EDLS)浓度,立体显微镜下手工微分离近球小管,液体闪烁计数器测定标记磷酸Ⅱ的方法检测近球小管Na+,K+-ATPase活性。结果①与AV3V注射人工脑脊液(aCSF) 的结果比较,AV3V注射AngⅡ后,血浆AngⅡ水平无显著变化,血清EDLS水平显著升高,近球小管Na+,K+-AT- Pase活性显著下降。②在AV3V注射沙拉新后,血浆AngⅡ水平无显著变化,血清EDLS水平显著降低,近球小管 Na+,K+-ATPase活性显著增加。结论 AngⅡ作用于AV3V的AngⅡ受体,引起近球小管Na+,K+-ATPase活性降低,AngⅡ的这一作用可能与促进EDLS的释放有关。

Objective The present study was designed to explore both the effect and the access of the intrinsic brain renin-angiotensin system （RAS） in the anteroventral part of the third ventricle （AV3V） on Na＋ , K^＋ -ATPase activity of proximal tubule. Methods Studies were performed on anesthetized Wistar rats and AV3V microinjection waa carried out by a stainless steel tube planted on the accurate site in the rat brain through a stereotactic apparatus. Ang Ⅱ and EDLS levels in plasm or serum were assessed by radioimmunoassay （ILIA）. Renal proximal tubules were isolated by means of manual microdissection then a single tubule was incubated and the hydrolytic activity of Na^＋, K^＋-ATPase was determined using a radiochemical assay based on the measurement of Pi released from [ γ-32p] ATP by liquid scintillation counter（LSC）. Resuits Serum endogenous digitalis - like substance （ EDLS ） level increased obviously on 60th minute after administration of Ang Ⅱ （ P 〈 0.01 vs aCSF）. In contrast, a statistically significant decrease of the activity of Na^＋ K^＋ -ATPasc from rats proximal tubule was measured （ P 〈 0.01 vs aCSF）. These effects could be antagonized by microinjection of saralasin, an angiotensin receptor antagonist, into the AV3V. The alterations of plasma Ang Ⅱ level were not significantly different in all groups after administration of the same volume of Ang Ⅱ, Sat. or aCSF （ P 〉 0.05） . There was a negative linear correlation between the serum EDLS level and proximal tubule Na^＋, K^＋-aATPase activity （r = -0. 905, P 〈 0.01 ）. Conclusions The central Ang Ⅱ may stimulate and modulate EDLS release, acting directly upon AV3V which is an important receptive site for Ang H, consequently the Na^＋, K^＋-ATPase activity of renal cortex is alternated.