Renal 4 Flashcards
sources of H+ gain
from CO2 (oxidative metabolism or hypoventilation)
high protein diet
loss of bicarbonate in urine
sources of H+ loss
loss of H+ in urine (excess secretion of H+ to exhaust all bicarbonate)
primary buffer system of ECF
CO2/HCO3-
buffering is tightly regulated because most – are altered by small pH changes
protein transport and enzyme reaction
alkalosis H+ loss –
H+ loss exceeds gain
acidosis H+ gain
H+ gain exceeds loss
bicarbonate is – at the glomerulus
freely filtered
bicarbonate is extensively reabsorbed along –
PT, ALH, cortical collecting ducts
bicarbonate can be secreted along –
collecting ducts
bicarbonate reabsorption is an active process but there are – at the luminal membrane
no bicarbonate transporter
how is bicarbonate reabsorbed?
depends on secretion of H+ which combine in the lumen with filtered bicarbonate
water + CO2 =
carbonic acid
carbonic acid is immediately dissociated into –
bicarbonate and H+ ions
HCO3- moves down its concentration gradient and into the interstitial fluid and blood by –
facilitated transporters
as HCO3- moves into the interstitial fluid and blood, H+ are transported to –
tubular lumen
H+ transporters
H+ ATPase, H+/K+ ATPase, Na+/H+ transporter
secreted H+ combines with bicarbonate that was –
filtered at glomerulus
is there a net change in bicarbonate?
no
as long as there is sufficient bicarbonate, all secreted H+ will combine to form –
carbonic acid –> water and CO2
what happens when filtered bicarbonate is completely exhausted and there is none to form carbonic acid?
H+ combines with other weak acids like phosphates and sulfates
when H+ ions combine with other weak acids it then –
excreted in urine
when H+ combines with other weak acids (nonbicarbonate) –>
net gain of bicarbonate in interstitial fluid and blood
what happens to the [H+] in the plasma when H+ combines with other weak acids (nonbicarbonates)?
lowers [H+]
increased pH
metabolism of – by tubular cells contribute new bicarbonate to blood
glutamine
