Renal regulation of H+ ions Flashcards
What is the buffering system of H+ within cells?
Pi/ proteins (e.g. Hb) + H+ Hbuffer. H+ is locked up
What is the buffering system of H+ outside cells?
CO2 + H2O H2CO3 H+ + HCO3-
Which systems work together to regulate H+?
Renal and respiratory system
How do bicarbonate ions at the kidney decrease plasma H+?
H2O + CO2 –> H2CO3 –> H+ + HCO3- within epithelial cell; H+ is secreted into tubular lumen from epithelial cell; through H+ ATPase pumps/ H+/K+ ATPase pumps/ Na+/H+ countertransporters; H+ combines with filtered HCO3- –> H2CO3; HCO3- liberated within cell passes into plasma; H2CO3 diffuses into epithelial cell; HCO3- in plasma can bind to H+ in blood
How can phosphate alkalinise plasma?
H2O + CO2 –> H2CO3 –> H+ + HCO3- within epithelial cell; H+ is secreted into tubular lumen from epithelial cell; through H+ ATPase pumps/ H+/K+ ATPase pumps/ Na+/H+ countertransporters; H+ combines with filtered HPO4 2- –> H2PO4-; H2PO4- secreted; HCO3- liberated within cell passes into plasma;; HCO3- in plasma can bind to H+ in blood. Net gain in HCO3-, with loss of H+ = alkalination
How can glutamine alkalinise plasma?
Glutamine enters epithelial cell from tubular lumen w/ Na+; glutamine produces NH4+ and HCO3-; NH4+ into tubular lumen by counter transport with Na; new HCO3- into plasma
When does respiratory acidosis occur?
When a person breathes shallowly; when gas exchange is hampered by diseases (pneumonia, CF, emphysema)
How does the body compensate for respiratory acidosis?
Arterial and CSF chemoreceptors stimulated = respiratory rate increased = decreased PCO2; renal system compensates by secreting H+ and generating HCO3-; other buffer systems accept H+
When does respiratory alkalosis occur?
Common result of hyperventilation
How does the body compensate for respiratory alkalosis?
Arterial and CSF chemoreceptors inhibited = respiratory rate decreased = increased PCO2; renal system compensates by generating H+ and secreting HCO3-; other buffer systems release H+
How is metabolic acidosis compensated for?
Rate and depth of breathing are elevated, so CO2 levels fall, increasing pH; kidneys secrete H+ and retain/generate HCO3-
How is metabolic alkalosis compensated for?
Rate and depth of breathing are lowered, so CO2 levels rise, decreasing pH; kidneys generate H+ and excrete HCO3-
How does renal blood change during exercise?
Renal blood flow decreased
At what exercise intensities is GFR affected?
> 50% VO2max; only decreases down to 60% during maximal exercise
What occurs to renal function in a hot environment?
Blood flow and GFR is decreased
