Correct option is D
Explanation-
The kidney regulates reabsorption of water and sodium chloride (NaCl) in the nephron to control blood volume, pressure, and osmolality. Some substances inhibit reabsorption (i.e., promote excretion of Na⁺ and H₂O), and some stimulate reabsorption.
Option D - Norepinephrine
It is a sympathetic neurotransmitter which timulates Na⁺ and water reabsorption by activating α-adrenergic receptors, increasing renin secretion → RAAS activation → Aldosterone release and vasoconstriction of renal vessels.
So, norepinephrine increases water and salt reabsorption, unlike the others.
Incorrect options-
Option A - Urodilatin
A natriuretic peptide secreted by kidney cells.
Function: Inhibits Na⁺ and water reabsorption in the collecting duct.
Thus, it reduces reabsorption.
Option B - Uroguanylin
it is secreted by the gut, acts on kidneys. It binds to guanylate cyclase receptors in the nephron. It promotes natriuresis (Na⁺ excretion) and diuresis (water loss).
Thus , inhibits reabsorption.
Option C - Dopamine
In the renal tubules, dopamine acts as a natriuretic hormone. It reduces Na⁺ reabsorption by inhibiting Na⁺/K⁺ ATPase.
Thus , inhibits reabsorption.
So, option D - Norepinephrine is the correct answer.
