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14 Cards in this Set
- Front
- Back
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What is the osmolarity of the filtrate that enters the DCT from the ascending loop of Henle?
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It is hyposmolar to plasma
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Name three of the four functions of the DCT and the collecting ducts.
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1.ADH-dependent water reabsorption
2.aldo-dependent NaCl reabsorption 3.aldo-independent NaCl reabsorption 4.aldo-dependent K+ secretion |
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What channel is used to move Na+ from the lumen to the cell in the distal tubule? How is the channel activated?
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*ENaC
*aldosterone |
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How is Na+ moved from the cell to the interstitium in the distal tubule?
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Na+/K+ ATPase
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In the distal tubule, Na+ moves down its gradient from the lumen into the cell. How is the charge balanced?
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Passive diffusion of K+ from the cell to the lumen.
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Describe the structure of the ENaC. What binding sites does it feature?
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*multi-subunit channel
*apical sites bind amiloride which blocks the channel *gates on the cytoplasmic side are responsive to aldosterone |
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What are 2 mechanisms used by the alpha cells of the distal tubule to secrete H+?
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1.H+/K+ ATPase
2.specific primary transporter (H+ ATPase) |
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When CO2 enters an epithelial cell of the distal tubule it combines with water and forms H+ and HCO3-. What happens to the bicarbonate ion?
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It is moved to the interstitium via a HCO3-/Cl- ATPase antiporter.
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How do alpha cells of the distal tubule help the body cope with respiratory acidosis?
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The activity of K+/H+ ATPase and other H+ transporters is increased to increase the secretion of H+.
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What is the minimal urinary pH that can be attained?
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4.5
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What are the beta cells of the distal tubule? What transporters do they feature? During what condition are these cells most active?
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*HCO3- secreting cells
*HCO3-/Cl- ATPase moves HCO3- into the lumen *H+ ATPase moves H+ into the interstitium *respiratory alkalosis |
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The osmolarity of the filtrate in the medullary collecting duct can vary widely - what causes this? What is the range of osmolarity of this filtrate?
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*the presence of ADH
*80mOsm/L (no ADH) to 300mOsm/L (max ADH) |
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What are two ADH-dependent functions of the medullary collecting duct?
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1.ADH-dependent activation of AQP-2 for reabsorption of water
2.ADH-dependent expression of UT-1 for urea reabsorption |
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How does ADH affect the reabsorption of Na+ in the medullary collecting duct?
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It doesn't - ADH mediates only the reabsorption of water, independent of Na+.
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