Regulation of neonatal renal hemodynamics

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DESCRIPTION (provided by applicant): At birth, the newborn kidneys are functionally immature and exhibit higher vascular resistance and lower glomerular filtration rate (GFR) compared with adults. Renal immaturity put neonates at risk for kidney injury, especially when renal hemodynamics is altered by adverse perinatal events including hypovolemia, asphyxia, sepsis, and renal ischemia. Several areas of neonatal renal hemodynamics remain unexplored. In particular, mechanisms that control neonatal renal vascular tone and pathological alterations that result in hypoperfusion during acute kidney injury (AKI) are unclear. A growing body of evidence suggests that members of the transient receptor potential (TRP) family of ion channels contribute to the intrinsic regulation of vascular tone and organ blood flow. Whether TRP channels control neonatal renal vascular resistance and hemodynamics is unknown. The present application originates from preliminary findings suggesting that the vanilloid transient receptor potential (TRPV) subfamily, member 4 is expressed in neonatal preglomerular renal artery and arteriole myocytes and regulates myogenic vasoconstriction, regional kidney perfusion, and GFR. Data from our pilot studies also suggest that alterations in renal vascular TRPV4 channel expression are associated with kidney hypoperfusion in renal ischemia/reperfusion-induced neonatal AKI. The overarching hypothesis of this proposal is that activation of vascular myocyte TRPV4 channels contributes to neonatal renal blood flow autoregulation, and that alterations in renal vascular myocyte TRPV4 channel expression and activity amplify kidney hypoperfusion in neonatal AKI. To address this hypothesis, three Specific Aims will be studied using newborn pigs. We will test the hypotheses that: 1. Intravascular pressure activates myocyte TRPV4 channels, leading to membrane depolarization and vasoconstriction in neonatal renal preglomerular arteries, 2. Myocyte TRPV4 channels regulate neonatal renal microcirculation, GFR, and electrolyte homeostasis, and 3. Renal ischemia-reperfusion in neonates upregulates arterial myocyte TRPV4 channel expression and activity, leading to hypoperfusion and a reduction in GFR. This application will identify TRPV4 channels as an important modulator of glomerular functions in neonates.