Renal Transport Mechanisms Flashcards
What is reabsorption powered by?
the Na-K-ATPase
what are the symporters associated with Na+?
glucose, amino acids, Pi, and HCO3-
what are the antiporters associated with Na+?
H+ and organic solutes
How does Na+ cross the basolateral border?
via the Na-K-ATPase
what transporter does the Na-glucose use on the apical membrane in the PCT?
the SGLT
what transporter/exchanger does the H+/Na+ use on the apical membrane in the PCT?
the NHE
what transporter does glucose use on the basolateral membrane?
GLUT
How is water reabsorbed transcellularly in the PCT?
via AQP channels
how is water reabsorbed paracellularly in the PCT?
passively
where does most reabsorption of Mg2+ take place?
in the TAL
What is present on the apical membrane of the TAL?
NKCC2 and ROMK channels
How does Na get out of the TAL cells?
through the Na-K-ATPase
how does Cl- get out of the TAL cells?
through a Cl- channel
how does K+ get out of the TAL cell?
either through a K+ channel on the basolateral membrane or through the ROMK channel that is on the apical membrane and back into the tubular lumen
What is the result of the K+ being secreted back into the tubular lumen of the TAL through the ROMK?
there will be a + charge build up in the TAL especially as we ascend
what does the buildup of the positive charge in the TAL cause?
Ca2+ and Mg2+ will squeeze out through paracellular diffusion
what is the most important site for regulation of the nephron?
the distal tubule
what are the cell types involved in the distal tubule?
principal cells, alpha-intercalated cells, and beta-intercalated cells
What do the principal cells reabsorb?
Na+ and H2O
what do the principal cells secrete?
K+
what do the alpha intercalated cells reabsorb?
K+ and HCO3-
what do the alpha intercalated cells secrete?
H+
what do the beta intercalated cells reabsorb?
H+ and Cl-
what do the beta intercalated cells secrete?
K+ and HCO3-
What is the concentration of the tubular fluid in the DCT?
since the DCT is impermeable to H2O and NaCl is continuing to be reabsorbed, the tubular fluid in the DCT becomes diluted
how does NaCl cross the apical membrane in the DCT?
via the Na-Cl-cotransporter (NCC)
What is the NCC sensitive to?
thiazide
How does Ca2+ cross the apical border in the DCT?
via the TRPV5 channel
How does Ca2+ cross the basolateral membrane in the DCT?
via the Na-Ca exchanger (NCE)
where are the principal cells located?
in the late distal tubule and collecting ducts
What is located on the apical membrane of the principal cell of the late distal tubule/collecting duct/ how is Na+ reabsorbed in the principal cells?
via the ENaC
What is located on the apical membrane of the principal cell of the late distal tubule/collecting duct that helps with K+ secretion?
an ROMK channel
What effect does aldosterone have on the principal cells?
aldosterone is going to increase the expression of the ENaC and Na-K-ATPase, which increases Na+ reabsorption and increases K+ secretion
How is K+ secreted in the principal cells and beta-intercalated cells?
passive diffusion out of the cell into the tubular lumen or through ROMK channels or BK channels
how do alpha-intercalated cells reabsorb K+?
through a H-K-ATPase on the apical membrane to get into the cell and then it passively diffuses across the basolateral membrane
