The renal cortical microcirculation delivers blood to the glomerular capillaries, where blood is filtered into the nephron. Pre- and postglomerular arteriolar tone is closely regulated to maintain a sufficient filtering pressure. The systems that control resistance of these arterioles remain a rich source of investigation. The goals of these studies are to better understand the physiology of glomerular blood flow and the potential dysfunctions that may contribute to renal failure and hypertension. Advances have been made both in methods to study these small-resistance vessels, such as intravital microscopy and isolated perfused afferent arteri-oles, and in studies of the hormones that regulate arteriolar resistance.
Afferent arteriole: The small artery leading into the glomerular capillary, providing the major vascular resistance in the kidney.
Efferent arteriole: The smallest artery in the cortex, which emerges from the glomerular capillary and leads to either a peritubular capillary (in the outer cortex) or vasa recta (in the juxtamedullary cortex). This vessel has a relatively high resistance capacity.
Glomerular capillary: A capillary containing an intricate network of branches and anastomoses, where the filtration of the fluid component of blood passes into the nephron. Located only in the renal cortex.
Renal vascular resistance: The change in hydrostatic pressure due to the tone of the downstream vasculature.
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4. Inscho, E. W., and Cook, A. K. (2002) P2 receptor-mediated afferent arteriolar vasoconstriction during calcium blockade. Am. J. Physiol. Renal Physiol. 282(2), F245-F255.
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10. Radermacher, J., Mengel, M., Ellis, S., Stuht, S., Hiss, M., Schwarz, A., Eisenberger, U., Burg, M., Luft, F. C., Gwinner, W., and Haller, H. (2003). The renal arterial resistance index and renal allograft survival. N. Engl. J. Med. 349(2), 182-184.
William J. Welch has worked extensively on intrarenal hormones that regulate tubuloglomerular feedback and its effect on renal function. He has used in vivo micropuncture to access the renal cortical vasculature and cortical nephrons. The interaction between single nephron function and vascular consequences has been the primary focus of his more than 60 published studies. He has used both normal and hypertensive models to show modu-latory roles for angiotensin II, thromboxane, nitric oxide, and superoxide in the control of GFR.
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