Q82: Hyperosmolarity of renal medulla is facilitated by all except. - Excretion - Veterinary Physiology- ICAR JRF/SRF 2024 | Agrigyan

• Mechanisms of Medullary Hyperosmolarity:
• The renal medullary osmotic gradient ($300\text{ up to }1200\text{ mOsm/kg}$) is established and maintained by:
• Active NaCl reabsorption by the thick ascending limb of Henle's loop into the medullary interstitium.
• Recirculation and medullary trapping of urea from inner medullary collecting ducts via UT-A1/UT-A3 transporters.
• Sluggish medullary blood flow through the hairpin vasa recta (countercurrent exchangers) preventing solute washout.
• Calcium Exclusion: Medullary $Ca^{2+}$ concentration plays NO role in generating the hyperosmotic gradient [Option 4].

Correct option: (4) Increased medullary Ca?*