As the glomerular filtrate passes through the uriniferous tubule, ions and water are exchanged (actively and passively) with the renal interstitium. These exchanges result in the filtrate being isotonic, hypotonic or hypeonic relative to blood plasma. What would be the tonicity of the filtrate passing through the renal capsular (Bowman's) space?
High-Yield Explanation
Filtration in the renal corpuscle provides an isotonic (= isosmotic) ultrafiltrate of blood plasma that enters Bowman's space. Filtrate leaving the coical collecting tubules, because of the presence of ADH (= antidiuretic hormone) becomes hypeonic (= hypoosmotic) by the time it reaches medullary collecting tubules. The filtrate approaching the distal convoluted tubules from the loop of Henle, on the other hand, even in the presence of ADH, becomes hypotonic (= hyperosmotic). Ref: Reilly R.F., Jackson E.K. (2011). Chapter 25. Regulation of Renal Function and Vascular Volume. In L.L. Brunton, B.A. Chabner, B.C. Knollmann (Eds),Goodman & Gilman's The Pharmacological Basis of Therapeutics, 12e.