PURINERGIC REGULATION OF THE RENAL MICROVASCULATURE

肌源性和微管小球反馈对自身调节的双重作用已被普遍接受，然而，涉及的化学信使(S)、受体和信号通路仍不清楚。在过去的5年里，我们提供了令人信服的证据，证明P2嘌呤受体的激活可以显著影响肾微血管功能。基于ATP激活的P2受体通过选择性地调节肾小球前阻力而参与自身调节行为的观察，我们推测，ATP介导的P2受体激活提供了将血流动力学刺激转化为自身调节反应的“化学信号”。在下一个资助阶段，我们希望通过确定ATP影响肾小球前微血管功能的机制，以及通过探索P2受体在肾脏自律行为的肌源性和转化生长因子介导的成分中的参与，来建立这些令人兴奋的观察结果。我们将使用延髓旁肾单位标本直接确定P2受体在肌源性和转化生长因子介导的自体调节反应中的作用。这些研究将包括表现出正常自我调节行为的血压正常的动物和自我调节能力受损的高血压动物。我们还将探讨局部释放的内皮因子对P2受体激活的肾小球前反应的旁分泌影响。这些研究将解决与正常肾脏相关的特定肾脏血流动力学问题，以及与高血压状态下观察到的肾脏微血管功能障碍相关的肾脏损害。我们将通过研究新鲜分离的肾小球前微血管平滑肌细胞中P2受体激活所触发的细胞内信号通路和膜电流，将从完整的传入小动脉获得的功能反应扩展到细胞水平。总而言之，这些研究结果将全面了解肾微血管P2受体对传入小动脉肌源性和转化生长因子介导的自身调节反应的作用；并将揭示在正常血压和高血压状态下，P2受体激活的细胞内信号级联调节传入小动脉功能。

The dual contribution of myogenic and tubuloglomerular feedback (TGF) influences to autoregulation is generally accepted; however, the chemical messenger(s), receptors and signaling pathways involved remain unknown. In the last 5 years, we have provided compelling evidence that P2 purinoceptor activation can significantly impact renal microvascular function. Based on the observation that P2 receptor activation by ATP participates importantly in autoregulatory behavior by selectively modulating preglomerular resistance, we hypothesize that ATP-mediated P2 receptor activation provides the "chemical signal" for transducing hemodynamic stimuli into autoregulatory responses. In the next period of funding, we wish to build on these exciting observations by determining the mechanisms by which ATP influences preglomerular microvascular function, and by exploring the involvement of P2 receptors in the myogenic and TGF-mediated components of renal autoregulatory behavior. We will directly determine the involvement of P2 receptors in myogenic and TGF-mediated autoregulatory responses using the juxtamedullary nephron preparation. These studies will include normotensive animals which exhibit normal autoregulatory behavior and hypertensive animals with impaired autoregulatory capability. We will also explore the paracrine influence of locally released endothelial factors on the preglomerular responses to P2 receptor activation. These studies will address specific renal hemodynamic issues relevant to normal kidneys and the renal damage associated with the renal microvascular dysfunction observed in hypertensive states. We will extend the functional responses obtained with intact afferent arterioles to the cellular level by examining the intracellular signaling pathways and membrane currents invoked by P2 receptor activation in freshly isolated, preglomerular microvascular smooth muscle cells. Collectively, the results of these studies will provide a comprehensive understanding of the contribution of renal microvascular P2 receptors to myogenic and TGF-mediated autoregulatory responses by afferent arterioles; and will reveal the intracellular signaling cascades invoked by P2 receptors to regulate afferent arteriolar function in normotensive and hypertensive states.