SM 191a/192a - Functions of the Renal Tubules I and II Flashcards

1
Q

Activation of the CaSR [downregulates/upregulates] flow through the Na+/K+/2Cl- cotransporter

Explain

A

Activation of the CaSR downregulates flow through the Na+/K+/2Cl- cotransporter

This decreases the + to - gradient generated by the cotransporter that pulls Ca2+ into the interstitum, thus reducing the force that drives Ca2+ reabsorption

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2
Q

How is the inner-medullary collecting duct similar to the cortical collecting duct?

How is it different?

A
  • Similar:
    • Na+ reabsorption pathway
    • K+ secretion pathway
    • Na+ reabsorption and K+ secretion are reciprocal
    • Water channels responsive to ADH
  • Different:
    • Medullary has ANP receptor on basolateral membrane; when bound to ANP, inhibits Na+ reabsorption
      • Promotes naturesis
    • Medullary has Urea transporter on apical membrane; reabsorbs urea, recycled back into the interstitium
      • Contributes to high interstitial osmolality
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3
Q

Competition for which transport protein leads to many drug-drug interactions?

A

P-gp

In the proximal convoluted tubule
(the primary site of secretion for drugs and drug metabolites)

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4
Q

Where in the kidney tubule does transcellular Ca2+ reabsorption occur?

Through which protein?

A

Distal covoluted tubule

  • Apical
    • TRPV5 channel
  • Basolateral
    • Ca2+/3Na+ exchanger
      • Driven by Na+ gradient into the cell
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5
Q

What are the effects of aldosterone binding to its cytoplasmic receptor?

A

Aldoserone/receptor complex is transported to the nucleus

  • Acts as a transcription factor
    • More Na+/K+ ATPases
    • More ENaC (Na+ channels)
    • More ROMK (K+ channels)
  • -> increased Na+ reabsorption, K+ secretion via…
    • Short-term mechanisms
      • Increased SGK1 activity -> phosphorylates NEDD-2
      • P-NEDD-2 cannot retrieve ENaC from the membrane
      • => More ENaC to reabsorb Na+
    • Later mechanisms
      • Increased surface area of basolateral membranes
      • -> Inreased Na+/K+ ATPase activity
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