Nephron Function





Summary By Transport Process




TABLE C.1

Na + and Cl Reabsorption
























Nephron Segment Mechanism Regulation
Proximal tubule Na + -H + antiport, Na + -solute symporters, Cl -HCO 3 antiporter, Na + -glucose symporters, paracellular ↓ ECF volume (+), ↑ ECF volume (–)
Angiotensin II (+)
Sympathetic nerves (+)
Epinephrine (+)
Dopamine (–)
Starling forces (+/–)
Henle’s loop
Thin descending limb
Thin ascending limb
Thick ascending limb
None
Paracellular
Na + -K + -2Cl symporter, Na + -H + antiporter, Cl -HCO 3 + antiporter
Aldosterone (+)
Sympathetic nerves (+)
Early distal tubule Na + -Cl symporter Aldosterone (+)∗
Sympathetic nerves (+)
Angiotensin II (+)
Late distal tubule and collecting duct (ASDN) Na + channel Aldosterone (+)
Sympathetic nerves (+)
Angiotensin II (+)
ANP, BNP, urodilatin (–)

ANP, Atrial natriuretic peptide; ASDN, aldosterone-sensitive distal nephron; BNP, brain natriuretic peptide; ECF, extracellular fluid; (+), stimulation; (–), inhibition; (∗), indirect effect.


TABLE C.2

K + Reabsorption
























Nephron Segment Mechanism Regulation
Proximal tubule Paracellular ↓ ECF volume (+)
↑ ECF volume (–)
Henle’s loop
Thin descending limb
Thin ascending limb
Thick ascending limb
None
None
Na + -K + -2Clˉ symporter
Aldosterone (+)
Early distal tubule None
Late distal tubule and collecting duct H + -K + -ATPase Dietary K + depletion (+)

ATPase, Adenosine triphosphatase; ECF, extracellular fluid; (+), stimulation; (–), inhibition.


TABLE C.3

K + Secretion
























Nephron Segment Mechanism Regulation
Proximal tubule None
Henle’s loop
Thin descending limb
Thin ascending limb
Thick ascending limb
None
None
None
Early distal tubule None
Late distal tubule and collecting duct K + channels, K-Cl symporter Plasma [K + ] (+)
Aldosterone (+)
AVP (+)
Flow rate (+)
Acid-base balance (+/–)
Glucocorticoids (+)

AVP, Arginine vasopressin; (+), stimulation; (–), inhibition.


TABLE C.4

H + Secretion ( <SPAN role=presentation tabIndex=0 id=MathJax-Element-1-Frame class=MathJax style="POSITION: relative" data-mathml='HCO3−’>HCO3HCO3
HCO3−
HCO3
HCO 3 −
Reabsorption)
























Nephron Segment Mechanism Regulation
Proximal tubule Na + -H + antiporter, H + -ATPase ↑ Filtered load of <SPAN role=presentation tabIndex=0 id=MathJax-Element-2-Frame class=MathJax style="POSITION: relative" data-mathml='HCO3−’>HCO3HCO3
HCO3−
HCO3
HCO 3 −
(+)
↓ ECF volume (+)
↑ P co 2 (+)
↓ Plasma [ <SPAN role=presentation tabIndex=0 id=MathJax-Element-3-Frame class=MathJax style="POSITION: relative" data-mathml='HCO3−’>HCO3HCO3
HCO3−
HCO3
HCO 3 −
] (+)
Endothelin (+)
Glucocorticoid (+)
Angiotensin II (+)
Henle’s loop
Thin descending limb
Thin ascending limb
Thick ascending limb
None
None
Na + -H + antiporter, H + -ATPase
↑ P co 2 (+)
↓ Plasma [ <SPAN role=presentation tabIndex=0 id=MathJax-Element-4-Frame class=MathJax style="POSITION: relative" data-mathml='HCO3−’>HCO3HCO3
HCO3−
HCO3
HCO 3 −
] (+)
Early distal tubule Na + -H + antiporter, H + -ATPase ↑ P co 2 (+)
↓ Plasma [ <SPAN role=presentation tabIndex=0 id=MathJax-Element-5-Frame class=MathJax style="POSITION: relative" data-mathml='HCO3−’>HCO3HCO3
HCO3−
HCO3
HCO 3 −
] (+)
Angiotensin II (+)
Endothelin (+)
Glucocorticoid (+)
Late distal tubule and collecting duct H + -ATPase, H + -K + -ATPase ↑ P co 2 (+)
↓ Plasma [ <SPAN role=presentation tabIndex=0 id=MathJax-Element-6-Frame class=MathJax style="POSITION: relative" data-mathml='HCO3−’>HCO3HCO3
HCO3−
HCO3
HCO 3 −
] (+)
Aldosterone (+)
Angiotensin II (+)
Endothelin (+)
Glucocorticoid (+)

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Oct 10, 2019 | Posted by in NEPHROLOGY | Comments Off on Nephron Function
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