Additional Functions: Erythropoiesis and Vitamin D
VITAMIN D Vitamin D is a fat-soluble vitamin that can be acquired either from diet or from sunlight-induced conversion of epidermal fats. In either case, vitamin D undergoes numerous modifications…
Classic Distal Renal Tubular Acidosis
Classic dRTA is treated with alkali replacement. If treatment is not instituted early on, however, chronic kidney disease may occur secondary to nephrocalcinosis or uncontrolled nephrolithiasis with consequent obstruction. Of…
Proximal Renal Tubular Acidosis
In addition to acidosis, pRTA features hypokalemia because the nonreabsorbed bicarbonate produces a negative charge in the collecting duct lumen, promoting K+ secretion through ROM-K channels. If there is generalized…
Acid-Base Balance: Acidosis and Alkalosis
Acidosis directly up-regulates ammoniagenesis through various mechanisms. Hypokalemia also up-regulates ammoniagenesis, whereas hyperkalemia down-regulates it, likely because of the effects of basolateral H+/K+ exchange on intracellular pH. Angiotensin II also…
Tubuloglomerular Feedback and Renin-Angiotensin-Aldosterone System
AII also acts at the subfornical organ in the brain, located outside the blood-brain barrier, to promote the release of ADH (see Plate 3-17) and to stimulate thirst. Moreover, it…
Antidiuretic Hormone
EFFECTS ADH exerts multiple effects on the kidneys and cardiovascular system, which include the following: In collecting ducts, ADH binds to V2 receptors on the basolateral membrane of principal cells,…
Tubuloglomerular Feedback and Modulation of Renin Release
MECHANISMS OF TUBULOGLOMERULAR FEEDBACK The available evidence suggests that the macula densa, located at the end of the thick ascending limb, senses tubular flow based on the concentrations of sodium…
Urine Concentration and Dilution and Overview of Water Handling: Long-Looped Nephron (ADH Present)
Descending Thin Limb. The descending thin limb reabsorbs an additional fraction of the filtered water. There is a large gradient for water reabsorption from this segment even though it reabsorbs…
Urine Concentration and Dilution: Long-Looped Nephron (ADH Absent)
Because of the countercurrent multiplier system, there is a strong gradient for water reabsorption from the collecting duct that increases in strength toward the papillae. Because water reabsorption is a…
Secretion and Reabsorption: Fractional Excretion (Clearance Ratios)
SECRETION AND REABSORPTION (Continued) QUANTIFYING REABSORPTION AND SECRETION One means of assessing the secretion or reabsorption profile of a particular solute is to examine its changing concentration along the length…
