Liclican Elvira L, McGiff John C, Pedraza Paulina L, Ferreri Nicholas R, Falck John R, Carroll Mairead A
Department of Pharmacology, New York Medical College, Valhalla, 10595, USA.
Am J Physiol Renal Physiol. 2005 Aug;289(2):F386-92. doi: 10.1152/ajprenal.00421.2004. Epub 2005 Apr 5.
Cytochrome P-450 (CYP)-dependent epoxyeicosatrienoic acids (EETs) dilate rat preglomerular microvessels when adenosine(2A) receptors (A(2A)R) are stimulated. As high salt (HS) intake increases epoxygenase activity and adenosine levels, we hypothesized that renal adenosine responses would be greater in HS-fed rats. Male Sprague-Dawley rats were fed either HS (4.0% NaCl) or normal salt (NS; 0.4% NaCl) diet. On day 8, isolated kidneys were perfused with Krebs' buffer containing indomethacin (10 microM) and L-NAME (200 microM) and preconstricted to approximately 150 mmHg with infusion of phenylephrine (10(-7) M). Renal effluents were extracted for analysis of eicosanoids by gas chromatography-mass spectrometry. Bolus injections of the stable adenosine analog 2-chloroadenosine (2-CA; 0.1-10 microg) resulted in dose-dependent dilation; at 10 microg, perfusion pressure (PP) was lowered to a greater extent in the kidneys of HS rats compared with NS rats (-60 +/- 4 vs. -31 +/- 8 mmHg; P < 0.05) and the area of response was increased (27 +/- 6 vs. 9 +/- 4 mm(2); P < 0.05), as was EET release (132 +/- 23 vs. 38 +/- 18 ng; P < 0.05). HS treatment increased A(2A)R and CYP2C23 protein expression. A selective epoxygenase inhibitor, MS-PPOH (12 microM), significantly reduced the response to 2-CA in HS rats; PP, area of response, and EET release decreased by 40, 70, and 81%, respectively, whereas lesser changes were evident in NS kidneys. Thus the greater vasodilator response to 2-CA seen in kidneys obtained from HS-fed rats was mediated by increased EET release. As EETs are renal vasodilator and natriuretic eicosanoids, interactions between adenosine and EETs may contribute to the adaptive response to HS intake.
当腺苷（2A）受体（A（2A）R）受到刺激时，细胞色素P-450（CYP）依赖性环氧化二十碳三烯酸（EETs）可使大鼠肾小球前微血管扩张。由于高盐（HS）摄入会增加环氧化酶活性和腺苷水平，我们推测HS喂养大鼠的肾脏腺苷反应会更强。将雄性Sprague-Dawley大鼠分为两组，分别给予HS（4.0%氯化钠）或正常盐（NS；0.4%氯化钠）饮食。在第8天，将分离的肾脏用含吲哚美辛（10微摩尔）和L-硝基精氨酸甲酯（200微摩尔）的 Krebs缓冲液灌注，并用去氧肾上腺素（10^-7摩尔）灌注使肾脏预收缩至约150毫米汞柱。通过气相色谱-质谱法提取肾流出液以分析类花生酸。静脉注射稳定的腺苷类似物2-氯腺苷（2-CA；0.1 - 10微克）可导致剂量依赖性扩张；在10微克时，与NS大鼠相比，HS大鼠肾脏的灌注压（PP）下降幅度更大（-60±4对-31±8毫米汞柱；P<0.05），反应面积增加（27±6对9±4平方毫米；P<0.05），EET释放量也增加（132±23对38±18纳克；P<0.05）。HS处理增加了A（2A）R和CYP2C23蛋白表达。一种选择性环氧化酶抑制剂MS-PPOH（12微摩尔）显著降低了HS大鼠对2-CA的反应；PP、反应面积和EET释放分别下降了40%、70%和81%，而NS大鼠肾脏的变化较小。因此，HS喂养大鼠肾脏中对2-CA更强的血管舒张反应是由EET释放增加介导的。由于EETs是肾血管舒张剂和利钠类花生酸，腺苷与EETs之间的相互作用可能有助于对HS摄入的适应性反应。
