GLOMERULI AND MICROVESSELS OF THE RABBIT KIDNEY CONTAIN BOTH ADENOSINE-A1 AND ADENOSINE-A2 RECEPTORS
GLOMERULI AND MICROVESSELS OF THE RABBIT KIDNEY CONTAIN BOTH ADENOSINE-A1 AND ADENOSINE-A2 RECEPTORS
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DOI：
10.1007/bf00165560
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发表时间：
1987-04-01
影响因子：
3.6
通讯作者：
SCHUTZ, W
中科院分区：
文献类型：
--
作者：
FREISSMUTH, M;HAUSLEITHNER, V;SCHUTZ, W
用胶原酶分散分离兔肾皮质，不连续蔗糖梯度纯化肾小球、微血管和肾小管。与(-)[125I]N6-(4-hydroxyphenylisopropyl)-adenosine([125I]HPIA)的结合实验提供了肾小球和微血管部分存在A1-腺苷受体的证据。肾小球与[~(125)I]HPIA结合的饱和等温线为单相，其Kd值为1.3nmol/L，Bmax为7.7fmol/mg蛋白。在动力学实验中，缔合速率常数为4.9倍。10~5(摩尔/L)~(-1)S~(-1)，解离速率常数为4.3倍。得到10~(-4)S~(-1)，其解离常数Kd值为0.9nmol/L，腺苷类似物取代[~(125)I]HPIA，与A1-腺苷受体的结合按效价顺序递减，并被甲基黄嘌呤类化合物抑制和GTP调节。微血管饱和实验测得Kd值为1.9nmoL/L，Bmax为13.4fmoL/mg蛋白。但对肾小球和微血管腺苷环化酶活性无明显抑制作用，但5‘-N-乙基羧胺-腺苷(NECA)和N-6-(R-苯异丙基)-腺苷(R-PIA)均能促进酶的活性，其EC50值分别为0.14u.mol/L和1.5u.mo./L。NECA的量效曲线右移10-微克/L 8-苯基茶碱。另一方面，双相曲线(通过刺激性受体激活的腺苷环化酶抑制)的计算机模拟表明，在存在刺激性腺苷受体的情况下，未能观察到A1-腺苷受体对腺苷环化酶活性的抑制可能是由于方法上的限制。结果表明，A1和A2腺苷受体均存在于兔肾小球和微血管中。提示这两种受体均参与肾素分泌的调控。
Rabbit renal cortices were fractionated by collagenase dispersion and glomeruli, microvessels and tubuli purified on a discontinuous sucrose gradient. Binding experiments with (-)[125I]N6-(4-hydroxyphenylisopropyl)-adenosine ([125I]HPIA) provided evidence for the presence of A1-adenosine receptors in the glomerular and microvascular fraction. With glomeruli, saturation isotherms for specific [125I]HPIA binding were mono-phasic with a KD of 1.3 nmol/l and a Bmax of 7.7 fmol/mg protein. In kinetic experiments, an association rate constant of 4.9 .times. 105 (mol/l)-1 s-1 and a dissociation rate constant of 4.3 .times. 10-4 s-1 were obtained, yielding a KD of 0.9 nmol/l. Adenosine analogs displaced [125I]HPIA binding with a rank order of potency typical of A1-adenosine receptors; furthermore, binding was inhibited by methylxanthines and modulated by GTP. Saturation experiments with the microvessels revealed a KD of 1.9 nmol/l and a Bmax of 13.4 fmol/mg protein. However, no inhibition of glomerular and microvascular adenylate cyclase activity could be demonstrated, but instead both 5''-N-ethylcarboxamido-adenosine (NECA) and N6-(R-phenylisopropyl)-adenosine (R-PIA) stimulated enzyme activity, with EC50 values of 0.14 .mu.mol/l and 1.5 .mu.mol/l, respectively. The concentration-response curve for NECA was shifted to the right (factor 9) by 10 .mu.mol/l 8-phenyltheophylline. On the other hand, computer simulation of biphasic curves (adenylate cyclase inhibition in the presence of activation via a stimulatory receptor) indicates that the failure to observe an A1-adenosine receptor-mediated inhibition of adenylate cyclase activity in the presence of stimulatory adenosine receptors may be attributable to methodological constraints. The results demonstrate that both A1- and A2-adenosine receptors are present in rabbit glomeruli and microvessels. It is suggested that both receptors are involved in the control of renin secretion.