TOPICS: Tubular fluid to plasma concentration ratio (TF/P), solute, inulin, creatinine, bicarbonate (HCO3-), para-aminohippuric acid (PAH), electrolytes, sodium (Na+) reabsorption, sodium (Na+) symporters, Na/K/2Cl cotransporter (NKCC), sodium/potassium (Na+/K+) exchanger, proximal convoluted tubule (PCT), distal convoluted tubule (DCT), loop of Henle, collecting duct (CD), thick ascending loop of Henle, thin ascending loop of Henle, fractional excretion of sodium (FENa), sodium (Na+) excreted, sodium (Na+) filtered, potassium (K+) reabsorption, filtered load (FL), principal cell, chloride (Cl-) reabsorption, alpha-intercalated cell, bicarbonate/chloride (HCO3-/Cl-) exchanger, calcium (Ca2+) reabsorption, sodium/chloride (Na+/Ca2+) antiporter, magnesium (Mg2+) reabsorption, urea reabsorption, urea secretion, dilution, hyperosmolar urine, hypoosmolar urine, nephron, corticopapillary osmotic gradient, urea recycling, urea transporter (UT1) channel, isotonic, hypertonic, hypotonic, antidiuretic hormone (ADH), osmotic gradient, vasa recta, countercurrent multiplication, osmolar gradient, collecting tubule