Page 190 - Color_Atlas_of_Physiology_5th_Ed._-_A._Despopoulos_2003

C. Excretion of titratable acids
pH
phosphate: 6.8 Late proximal: 6.6 8
Blood: 7.4
Urine, min: 4.5
pK of 8 H +
7
7
6
6
5
5 pH The Kidney and Acid–Base Balance II
pH 4
4 0
0 >0.99 0.8 0.6 0.4 0.2 <0.01
>0.99 0.8 0.6 0.4 0.2 <0.01 [HPO 4 ]/total phosphate
2–
2–
[HPO 4 ]/total phosphate
1 2
H excretion with phosphate Back titration with NaOH yields
+
+
(titratable acidity) amount of H -Ionen
D. Secretion and excretion of NH 4 + NH 3
From protein catabolism Henle’s loop Plate 7.15
≈1000 4 2Cl –
mmol/d +
NH 4 Collecting duct
+
NH 4 + HCO 3 – Urea +
NH 4
≈50 BSC
mmol/d H + H +
+
H buffering: NH 3
+
Glutamine 0 “Indirect H excretion”
Glutamate – – + Na + +
HCO 3 H K
1 NH 4 +
Secretion of Cortex:
+
NH 3 NH 4 <1 mmol/L
+
NH 3 NH 4
Proximal tubule See 4
2
Gluta- Gluta-
mine 0 mine 0
Glutaminase Na +
Na + + – 3
NHE 3 NH 4 Glu
+
NH 4
Glu - –
+ Dehydrogenase
NH 4
α-ketoglutarate 2–
H + Glucose Medulla
NH 3 NH 3 10 mmol/L
H + – H 2 O NH 3 NH 4 +
H + OH
–
HCO 3
CA II +
CO 2 Na
NHE 3 Excretion:
+ Na + + 25–50 mmol/d
NH 4 + NH 4 177
K +
NH 3 NH 4
Despopoulos, Color Atlas of Physiology © 2003 Thieme
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