- Which one of the following factors inhibits rennin secretion ?
(1) Increased level of plasma catecholamines.
(2) Increased blood pressure in the afferent arterioles leading to glomerulus.
(3) Increased activity of sympathetic nerves connected to kidney.
(4) Prostaglandins.
Renin secretion from juxtaglomerular cells of the kidney is a tightly regulated process crucial for maintaining blood pressure and fluid balance via the renin-angiotensin-aldosterone system (RAAS). Various factors stimulate or inhibit renin release. Understanding these regulators is important in physiology and pathophysiology of hypertension and kidney diseases.
Key Factors Influencing Renin Secretion
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Renin release is triggered primarily by:
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Decreased blood pressure sensed at afferent arterioles (baroreceptor mechanism)
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Reduced sodium chloride delivery detected by the macula densa
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Increased sympathetic nervous system activity via beta-1 adrenergic receptors.ncbi.nlm.nih+2
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Factors Inhibiting Renin Secretion
Among the options provided:
1. Increased level of plasma catecholamines
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Catecholamines, especially norepinephrine, stimulate renin release through beta-adrenergic receptors.
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Therefore, increased plasma catecholamines do not inhibit but stimulate renin secretion.
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So, option (1) is incorrect.
2. Increased blood pressure in afferent arterioles leading to glomerulus
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Increased pressure in afferent arterioles stretches baroreceptors that inhibit renin release.
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This negative feedback prevents excess RAAS activation when blood pressure is high.
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Thus, option (2) is correct as an inhibitor.
3. Increased activity of sympathetic nerves connected to kidney
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Sympathetic nervous system activation stimulates renin release via beta-1 adrenergic stimulation.
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So, increased sympathetic activity stimulates, not inhibits, renin secretion.
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Option (3) is incorrect.
4. Prostaglandins
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Prostaglandins (especially PGE2) produced in the kidney generally stimulate renin release by vasodilating afferent arterioles and promoting macula densa signaling.
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Thus, prostaglandins do not inhibit but promote renin secretion.
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Option (4) is incorrect.
Summary Table
Factor Effect on Renin Secretion Role Increased plasma catecholamines Stimulates Not inhibitor Increased afferent arteriole pressure Inhibits Inhibitor Increased sympathetic nerve activity Stimulates Not inhibitor Prostaglandins Stimulates Not inhibitor Conclusion
The factor that inhibits renin secretion among the options is:
(2) Increased blood pressure in the afferent arterioles leading to the glomerulus.
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