Question

which of the following induces renin secretion, constricts afferent arterioles, and reduces gfr and urine volume?
multiple choice
antidiuretic hormone
norepinephrine
aldosterone
angiotensin ii
parathyroid hormone

Explanation:

• Antidiuretic hormone: Mainly regulates water reabsorption in the collecting ducts, not directly inducing renin secretion in the described way.
• Norepinephrine: Can cause vasoconstriction but its role in the specific combination of inducing renin secretion (as part of a coordinated renal - hemodynamic response like in the renin - angiotensin - aldosterone system) is not as central as the correct option.
• Aldosterone: Is part of the renin - angiotensin - aldosterone system but its main action is on sodium and potassium reabsorption in the distal tubules, not directly constricting afferent arterioles in the initial step of the described process.
• Angiotensin II:
• Induces renin secretion (through a negative feedback loop in some cases, but also as part of the overall activation of the renin - angiotensin - aldosterone system where its formation stimulates further renin - related responses in a complex regulatory network).
• Is a potent vasoconstrictor of afferent (and efferent) arterioles.
• Reduces glomerular filtration rate (GFR) by constricting arterioles and also reduces urine volume by promoting sodium reabsorption (through its influence on aldosterone release and direct tubular effects).
• Parathyroid hormone: Regulates calcium and phosphate metabolism, not involved in the described renal hemodynamic and renin - related actions.

Answer:

Angiotensin II