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-m-Angiotensin-Aldosterone System

RENAL PHYSFOLOCY

Inhibilion

•‘O;

f Blood pressure f fluid volume | fłj-Sympatbetic ANP

■ ♦ Renin

i    ♦ Vasoconstriction

♦ Aldosterone----------------—

Mechanism* of Renin Release

JOeWA-CRA^o

Sympathetic nerve mechanism:

{Ji-Adrenergir nerves stimulale renin releasc (grecn arrowsf

°MM\|

|uxlaglomerular (|G) cells

•arnreceptor mechanism:

nereased pressure in afferent arteriole inhibits ««n release from JG cells (red arrows); dccreased pressure promotes renin release (green arrows)

Macula densa mechanism:

Increased NaCl in distal nephron inhibits renin release (red arrows); decreased load promotes renin release

Figurę 6.12 Renin-Anciotensin-Aldosterone System

"-*> kidney synthesizes and secretes the proteolytic enzyme renin in oporne to decreased blood pressure and fluid volume (upper ^ane/). Renin release ultimately results in increased levels of .-©otensin II (AID and aldosterone, both of which stimulalc NaCl ■d water reabsorption by the nephron i Ali acts on the proximal -hjIc and aldosterone acts on the collec ling duet). Ali is also a :otent vasoconstrictor. Thus. when blood pressure and fluid volume

are Iow, the renin angiotensiivaldosterone system acts to restore both. The renin-seereting juxtagloinerular cells art* located primarily in Ihe afferent arteriole (lower panel). These cells respond directly to changes m arterial pressure, alterations in sympathetic nerve activity, and to the delivery of NaCl to the macula densa. Abbreviations: ACŁ. Angiotensin<onverting enzyme; ANP, atrial natriuretic peptide.

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