Renal Regulation of H+ Flashcards
How does hypo- and hyperventilation affect H+?
Hypoventilation - net gain of H+
Hyperventilation - net loss of H+
How does the GI tract affect H+ concentration?
Vomitus - loss of H+
Diarrhea - gain of H+ (due to loss of bicarbonate)
What three processes are involved in regulation of Bicarbonate?
Conservation
Excretion
Replenishment
How is bicarbonate reabsorbed in the PT?
Converted to water and CO2 in the PT by Carbonic Anhydrase on the luminal membrane
Diffuses into the cell, converted back into bicarbonate
Crosses the BL via a Bicarb/Cl antiporter and an Na/3HCO3 symporter
How is bicarbonate secreted by intercalated cells?
HCO3/Cl antiporter on the apical membrane
Created by Carbonic Anhydrase within the cell
By what two mechanisms do the kidneys contribute new bicarbonate to the plasma?
Secretion of Hydrogen ions which combine with non-bicarbonate buffers supplied by filtration
Catabolism of glutamine in association with excretion of ammonium in the urine
What is the primary urinary buffer?
Phosphate
Describe the catabolism of glutamine and its role in H+ secretion
Glutamine is catabolized into ammonia in the PT ans secreted
Ammonia is reabsorbed in the thick ascending loop accumulates in the interstitium
NH4 is secreted by the CD, requiring the simultaneous secretion of H+
For each NH4 excreted, a new HCO3 is added back to the ECF
What is net acid secretion?
Kidneys’ net bicarbonate addition to or elimination from the body
NAE that is negative, loss of bicarb
NAE that is positive, gain of bicarb
How is NH4 excretion controlled?
Increased during acidosis and decreased during alkalosis
How is tubular H+ secretion controlled?
Increased PCO2 of respiratory acidosis and vice versa
Increased by local effects of decreases extracellular pH on the tubules, and vice versa
