Autoregulation, which is responsible for maintaining constant glomerular filtration rate (GFR) and renal blood flow (RBF), remains unaffected within the range of arterial blood pressure between 90 and 180 mm Hg. Various factors such as sympathetic nerves, catecholamines, angiotensin II, prostaglandins, nitric oxide (NO), endothelin, natriuretic peptides, bradykinin, and adenosine exert significant control over GFR and RBF when extracellular fluid volume (ECFV) is altered.

The following references provide further insights into the intricate functioning of the glomerulus, the podocyte biology, tubuloglomerular feedback-induced vasoconstriction, capillary fluid exchange, renal circulation and glomerular hemodynamics, and the structural organization of the kidney:

1. Patel A. The primary cilium calcium channels and their role in flow sensing. Pflugers Arch. 2015;467:157-165.
2. Pollak MR, et al. The glomerulus: the sphere of influence. Clin J Am Soc Nephrol. 2014;9:1461-1469.
3. Schlondorff J. How many Achilles’ heels does a podocyte have? An update on podocyte biology. Nephrol Dial Transplant. 2015;30: 1091-1097.
4. Schnermann J. Concurrent activation of multiple vasoactive signaling pathways in vasoconstriction caused by tubuloglomerular feedback: a quantitative assessment. Annu Rev Physiol. 2015;77:301-322.
5. Taylor AE, Moore TM. Capillary fluid exchange. Adv Physiol Educ. 1999;22:s203-s210.
6. Arendshorst WJ, Navar LG. Renal circulation and glomerular hemodynamics. In: Schrier RW, et al., eds. Diseases of the Kidney and Urinary Tract. 9th ed. Philadelphia: Lippincott Williams & Wilkins; 2012.
7. Dworkin LD, et al. The renal circulations. In: Taal MW, et al., eds. Brenner and Rector’s The Kidney. 9th ed. Philadelphia: Saunders; 2012.
8. Kriz W, Kaissling B. Structural organization of the mammalian kidney. In: Alpern RJ, et al., eds. Seldin and Giebisch’s The Kidney: Physiology and Pathophysiology. 5th ed. Philadelphia: Academic Press; 2012.
9. Lafayette RA, et al. Laboratory evaluation of renal function. In: Schrier RW, et al., eds. Diseases of the Kidney and Urinary Tract. 9th ed. Philadelphia: Lippincott Williams & Wilkins; 2012.
10. Madsen K, et al. Anatomy of the kidney. In: Taal MW, et al., eds. Brenner and Rector’s The Kidney. 9th ed. Philadelphia: Saunders; 2012.

After studying this chapter, you should be able to answer the following questions:

1. What are the three processes involved in urine production?
2. What is the composition of "normal" urine?
3. Along the nephron, where are the transport mechanisms responsible for NaCl reabsorption located?
4. In the proximal tubule, how is water reabsorption coupled with NaCl reabsorption?
5. Why is only solute reabsorbed by the thick ascending limb of Henle's loop, and not water?
6. What are the transport mechanisms involved in the secretion of organic anions and cations, and what is the physiological significance of these processes?
7. Define glomerulotubular balance and explain its physiological importance.
8. Name the major hormones that regulate NaCl and water reabsorption by the kidneys, and identify the nephron site where each hormone acts.
9. What is the aldosterone paradox?
4.
Autoregulation allows GFR and RBF to remain constant despite changes in arterial blood pressure between 90 and 180 mm Hg. When ECFV is altered, sympathetic nerves, catecholamines, angiotensin II, prostaglandins, NO, endothelin, natriuretic peptides, bradykinin, and adenosine exert substantial control over GFR and RBF.
Patel A. The primary cilium calcium channels and their role in flow sensing. Pflugers Arch. 2015;467:157-165.
Pollak MR, et al. The glomerulus: the sphere of influence. Clin J Am Soc Nephrol. 2014;9:1461-1469.
Schlondorff J. How many Achilles’ heels does a podocyte have? An update on podocyte biology. Nephrol Dial Transplant. 2015;30: 1091-1097.
Schnermann J. Concurrent activation of multiple vasoactive signaling pathways in vasoconstriction caused by tubuloglomerular feedback: a quantitative assessment. Annu Rev Physiol. 2015;77:301-322.
Taylor AE, Moore TM. Capillary fluid exchange. Adv Physiol Educ. 1999;22:s203-s210.
Arendshorst WJ, Navar LG. Renal circulation and glomerular hemodynamics. In: Schrier RW, et al., eds. Diseases of the Kidney and Urinary Tract. 9th ed. Philadelphia: Lippincott Williams & Wilkins; 2012.
Dworkin LD, et al. The renal circulations. In: Taal MW, et al., eds. Brenner and Rector’s The Kidney. 9th ed. Philadelphia: Saunders; 2012.
Kriz W, Kaissling B. Structural organization of the mammalian kidney. In: Alpern RJ, et al., eds. Seldin and Giebisch’s The Kidney: Physiology and Pathophysiology. 5th ed. Philadelphia: Academic Press; 2012.
Lafayette RA, et al. Laboratory evaluation of renal function. In: Schrier RW, et al., eds. Diseases of the Kidney and Urinary Tract. 9th ed. Philadelphia: Lippincott Williams & Wilkins; 2012.
Madsen K, et al. Anatomy of the kidney. In: Taal MW, et al., eds. Brenner and Rector’s The Kidney. 9th ed. Philadelphia: Saunders; 2012.
Upon completion of this chapter the student should be able to answer the following questions: 1.
What three processes are involved in the production of urine?
2.
What is the composition of “normal” urine?
3.
What transport mechanisms are responsible for NaCl reabsorption by the nephron? Where are they located along the nephron?
4.
How is water reabsorption “coupled” to NaCl reabsorption in the proximal tubule?
5.
Why are solutes but not water reabsorbed by the thick ascending limb of Henle’s loop?
6.
What transport mechanisms are involved in secretion of organic anions and cations? What is the physiological relevance of these transport processes?
7.
What is glomerulotubular balance, and what is its physiological importance?
8.
What are the major hormones that regulate NaCl and water reabsorption by the kidneys? What is the nephron site of action of each hormone?
9.
What is the aldosterone paradox?