27568 netter115

r

Volume expansion p

~r

i

Sympathetic

aclivily

1

■ | Renin •

| Na* resorption

[>ro\im,il

| Na'andH₂0 resorption in collecting duet

| Angiotensin I

). Perkins

MS, MFA

V.

Figurę 6.13 Response to Volume Expansion

The kidneys respond to an inerease in the volume ot the extracellular fluid (volume expansion) by inereasing their excretion of NaCI and water. The primary rnechanisms in this response are summarized. Enhanced NaCI excretion results from an inerease in the filtered load of NaCI (inereased GHR) and inhibition of NaCI reabsorption along the nephron. This occurs because the sympathetic: and renin-angiotensin aldoslerone system*. are suppressed and atrial natriuretic

peptide (ANP) secretion is stimulated. The aefions of ANP oppo-those of the renin-angiotensin-aldosterone system. ANP inerease*: GfR and inhibits collecting duet NaCI reabsorption. The kidney . produces its own natriuretic peptide called urodilatin, which cor -tributes to this response. Decreased levels of antidiuretic hormor-<ADHJ cauSe inereased water excrelion. Abbreviation: ACŁ. Angio«ensirvconverting enzyme.