S-27-1: THE ROLE OF KIDNEY IN BLOOD PRESSURE REGULATION

Abstract

The kidney plays important roles in homeostasis of body fluid and electrolyte balances as well as blood pressure (BP) regulation. For these, two functions are required. One is a stable and huge (150L/day) amount of glomerular filtration rate (GFR) in the face of large variations of BP and dairy salt intake, and the other is pressure natriuresis. Even if BP changed acutely, glomerular capillary pressure of each nephron is maintained relatively stale by myogenic response and tubuloglomerular feedback (TGF). When salt intake is changed, GFR is maintained by exquisitely precise and elegant interplays among the rein-angiotensin-aldosterone (RAA) system, TGF and connecting TGF (cTGF). The cTGF is a recently discovered intrinsic mechanism controlling glomerular hemodynamics. The pressure natriuresis plays a crucial role in the maintenance of body fluid volume, and its site of action is renal medulla. Blood supply to renal medulla is governed by descending vasa recta, the efferent arteriole of the juxtaglomerulus. In outer medulla, thick ascending limb of juxtamedullary nephron makes direct contact with descending vasa recta. Studies indicate that nitric oxide and oxidative stress produced by this tubular segment affect vascular tone of descending vasa recta, a phenomenon called tubulo-vascular crosstalk. The tubule-vascular crosstalk is implicated to play an important role in oxygen metabolism in such conditions as heart failure and high salt intake. In this presentation, I will discuss above mentioned mechanisms that control renal hemodynamics, sodium balances and BP.