Renal Flashcards
(249 cards)
1
Q
Which hormone does the kidney use to control RBC production?
A
Erythropoietin
2
Q
Why is plasma only 91% water?
A
Because proteins eg) albumin are very large
3
Q
What is Van’t Hoff’s equation?
A
Osmotic pressure = osmolarity x gas constant x absolute temp
4
Q
What is osmolality?
A
Osmoles per kg water (not osmoles per litres because 1 litre plasma isn’t 1 litre water)
5
Q
What does it mean that osmolality is “colligative”?
A
Proportional to number not type of particle
6
Q
Why do cells not contribute to colloid osmotic pressure?
A
They’re not dissolved
7
Q
What provides ECF osmolality?
A
NaCl
8
Q
What provides ICF osmolality?
A
K+, Cl- and impermeable ions
9
Q
What is crenation?
A
Shrinking around cytoskeleton
10
Q
How does cerebral swelling kill?
A
Compresses medulla so stops breathing, or compresses veins causing even more swelling
11
Q
How do you measure intracellular volume?
A
Total water - ECF volume
12
Q
Does cortex or medulla have rich blood supply and lots of mitochondria?
A
Cortex
13
Q
Does the afferent or efferent arteriole have baroreceptors?
A
Afferent
14
Q
What do the podocytes provide?
A
Fenestrated capillary, basement membrane, diaphragm between foot processes
15
Q
Why are podocytes negatively charged?
A
To repeal albumin
16
Q
Why do some cations remain in the plasma?
A
Becayse there are -ve proteins there so cations remain due to charge
17
Q
Filtration fraction = ?
A
glomerular filtration rate / renal plasma flow
18
Q
Why does the remaining plasma cause decreased net filtration pressure?
A
High proteins and % haematocrit
19
Q
Kidney flow = ?
A
Change in pressure / Ra + Re
20
Q
What does dilating afferent or constricting efferent cause?
A
Increased pressure but decreased flow
21
Q
Glomerular capillary pressure = ?
A
Venous pressure + AV pressure gradient x efferent resistance/total resistance
22
Q
What is the autoregulatory range?
A
Large blood pressure range across which the glomerular filtration rate doesn’t change
23
Q
What are the two ways to reduce flow?
A
Myogenic or tubulo-glomerular
24
Q
What is the myogenic mechanism to reduce flow?
A
High blood pressure stretches afferent so it constricts
25
What is the tubulo-glomerular feedback mechanism to reduce flow?
Macula densa senses NaCl uptake, releases ATP, stimulates afferent arteriole constriction
26
What do mesangial cells do?
Contract to reduce capillary membrane area
27
Why can severe muscle damage cause renal failure?
Myoglobin can block filtration pores
28
What is "clearance"?
Expresses rate of excretion as a function of plasma concentration
29
Clearance = ?
Rate of excretion / plasma concentration
30
What is excretion measured in?
moles/min
31
What is clearance measured in?
ml/min
32
Why do positive molecules have highest filterability?
Attracted to and pulled through membrane
33
Why do -ve molecules have higher filterability if they are very small?
Can slip through when small
34
What happens to clearance if renal handling is constant?
Stays the same because if plasma concentration is doubled then excretion rate is doubled
35
What does it mean if clearance is less than or greater than GFR?
If less then not freely filtered, if greater then must also be secreted
36
Rate of excretion = ?
GFR x plasma conc
37
Clearance = ?
GFR
38
Excretion = ?
urine production x urine concentration
39
Clearance = ?
urine production x urine concentration / plasma concentration
40
What is the filtration coefficient?
Product of surface area and hydraulic conductivity
41
What is the protein reflection coefficient?
Goes 0 (permeable) to 1 (impermeable)
42
What may reduce the filtration coefficient?
Filtration pores becoming blocked or mesangial cells contracting to reduce capillary membrane area
43
What may increase Pc - Pb?
Increased in UTI obstruction
44
How do you measure clearance?
Find something produced at a constant rate and freely excreted then use clearance = rate of excretion / plasma conc eg) creatinine
45
What does the clearance ratio compare?
The clearance of something to the clearance of inulin
46
What is the clearance ratio of PAH like? Why is this useful?
Greater than 1 because it's very efficiently secreted, so clearance of PAH is effective renal plasma flow (use Fick principle for this but need arterial and venous concentrations)
47
For protein channels, what is flux proportional to?
Electrochemical gradient ( x permeability)
48
What is the maximum rate of transport for carrier proteins called?
Transport maxima
49
Why doesn't NaCl concentration in tubule not change?
Water follows it
50
What are some possible anions in the Cl- anion exchanger?
OH-, HCO2-, HCO3-, oxalate or sulphate
51
Where is Cl- reabsorption greatest?
Late PCT
52
Which anions are secreted in the PCT?
Prostaglandins, cAMP, bile salts, drugs eg penicillin
53
Which cations are secreted in the PCT?
Creatinine, adrenaline, noradrenaline, dopamine and drugs eg morphine
54
How are -ve ions transported into a -ve cell?
Enters in exchange for an anion, anions are recycled because there's more Cl- to reabsorb than anions to secrete
55
What is the evidence for isotonic reabsorption?
Either inject inulin and use micropuncture to compare early and late PCT (PCT has higher conc) or use split oil drop to test how things are absorbed
56
What happens to anions in the tubule?
Protonated and are then uncharged so can diffuse back
57
Why is the tubule acidic?
Because of Na+/H+ exchanger
58
When is K+ released?
Exercise, acidosis (displaced by H+), dehydration (cellular shrinkage) and cell lysis
59
When is K+ taken in/ when does K+ conc decrease?
Hyperhydration, insulin, adrenaline
60
What happens to the ECG during hyperkalaemia?
QRS gets smaller because cardiac muscle gets inexcitable and T wave gets faster because of inwardly rectifying K+ channels
61
What happens to K+ during hypokalaemia?
T wave gets smaller and you get a U wave
62
Why do you get arrhythmias outside normal K+ range?
More excitable atria and slower repolarisations because of changes in channel conductance and inwardly rectifying channels
63
Which is the main regulatory hormone of K+?
Aldosterone
64
In what area is aldosterone important for Na+ reabsorption?
DCT
65
What stimulates aldosterone?
Angiotensin II
66
How does ADH affect K+ control?
Keeps excretion constant but alters concs, increases SK activity and reduces tubular flow rate
67
Why is renal K+ control slow?
Only 2% of body K+ is in the ECF
68
What detects high extracellular K+? WHat does it release?
Zona glomerulosa - aldosterone
69
Which pump does aldosterone stimulate
Na+/K+
70
Which hormones stimulate Na+/K+ pump?
Aldosterone, adrenaline, insulin
71
How does insulin stimulate Na+/K+ pump?
Stimulates Na+/glucose which stimulates Na+/K+
72
What causes hypokalaemia?
Diuretics, diarrhoea, vomiting, reduced food intake
73
What causes hyperkalaemia?
Renal failure, doctor error, cell lysis, acidosis
74
How do you treat hyperkalaemia?
Ca2+ will stabilise membrane potentials and adding glucose and insulin makes Na+/K+ pump work faster
75
How does plasma pH affect plasma conc Ca2+?
Influences charge on albumin - albumin binds to Ca2+ so if H+ changes then plasma conc of Ca2+ will change
76
What happens to bone during chronic acidosis?
It buffers H+ so get demineralisation
77
What are the symptoms of acidosis?
Central sympotoms - nausea, fatigue, confusion, coma, death
78
What are the symptoms of alkalosis?
Muscle symptoms - hypokalaemia, hypocalcaemia because more -ve plasma buffers, hyperexcitability, cramps, tetany
79
Metabolism of which amino acids produces H2SO4?
Cysteine and methionine
80
Metabolism of which amino acids produces HCO3-?
Aspartate and glutamate
81
Why is it more common to be pushed toward acid production?
Can't be breathed out like CO2 can?
82
What are some fast extracellular buffers?
HCO3-, HPO42-, bone and plasma proteins
83
What are some slow intracellular buffers?
HCO3-, HPO42-, proteins esp. histidine
84
Why must kidney produce new HCO3-?
Needs to be added to reduce losses to metabloic acids but there isn't enough so kidney has to produce it
85
What is a problem with HCO3- production?
Would produce H+ so must be secreted and buffered
86
What is the main filtrate buffer?
HPO42-
87
How is the kidney a net bicarb producer but almost none is excreted?
H+ secreted, HCO3- reabsorbed as CO2, so more bicarb produced because if CO2 is increasing then too much bicarb is being used to buffer H+
88
Which cells secrete bicarb?
Type B intercalated in the collecting duct
89
Which amino acid is bicarb produced from?
Glutamine
90
What is ammoniagenesis?
Making ammonia from glutamine in PCT
91
What happens to the glutamine in ammonia genesis?
Glutamine > glutamic acid > alphaKG > Krebs cycle > glucose. SO get 2HCO3-, excrete 2NH4+ and make half a glucose
92
What happens to the ammonium produced from glutamine?
Splits to ammonia in cell and recombined in tubule - now trapped so excreted
93
Where is NH4+ reabsorbed?
Ascending limb
94
What does NH4+ substitute for on which transporter?
K+ on the Na+-K+-2Cl- co-transporter
95
What do osmoreceptors in the hypothalamus detect?
Osmotic pressure, not [Na+]
96
What is AVP?
Arginine vasopressin (ADH)
97
Where is ADH broken down?
PCT
98
What are the two ADH receptors?
V1 = vascular smooth muscle, low affinity V2 = collecting duct, high affinity
99
Which circulatory factors affect ADH production?
Arterial baroreceptors can stimulate or inhibit release, so can cardiopulmonary receptors via vagus and glossopharyngeal
100
Which osmoregulatory factors affect ADH release?
Nervous inputs from GI tract via vagus, liver osmoreceptors detecting water absorption from food
101
What kind of neurone terminals do act pots from osmoreceptors arrive at?
Magnocellular
102
What kind of neurones does ADH travel down?
Magnocellular
103
WHich organ contains the osmoreceptors?
OVLT (organum vasculosum laminae terminalis)
104
How does osmodetection link cell size to ion channel activity?
When cells shrink they depolarise to increase action potential frequency because stretch-inactivated non-selective cation channels show increased activity
105
How do you show osmotic pressure regulated ADH release?
Make diuresis easy to detect by stomach-tubing water. Exteriorise carotid arteries to form carotid loops so solutions can be introduced here not into veins. Hypertonic NaCl caused reduction in urine flow rate in carotid artery but not vein. Urea had no effect.
106
What is the integrated response of osmoreceptors and circulatory stretch receptors?
Largest changes in plasma ADH if osmotic pressure and blood pressure are reduced
107
Which aquaporins does the adluminal membrane always have?
AQP3 and AQP4
108
If ADH decreases, which aquaporins is removed by endocytosis?
AQP2
109
What's the maximum urine osmotic pressure?
1200mosm
110
What are the main waste solutes?
SO4 2- and HPO4 2-
111
What is the mechanism of activation of AQP2?
ADH > V2 receptor (GPCR) > adenyl cyclase > cAMP > PKA > vesicles phosphorylated using serine 256 > fuse with collecting duct luminal membrane
112
How does ADH increase urea permeability of medullary collecting duct and thin ascending limb?
Stimulating phosphorylation and activation of urea transporters in luminal membrane
113
What is the main urea transporter?
UT-A1
114
What is the luminal/adluminal membrane urea transporter?
UT-A3
115
What is the urea transporter in the thin descending limb?
UT-A2
116
What does angiotensin stimulate?
Na+/H+ exchange
117
What does aldosterone stimulate
K+/H+-ATPase
118
What pH is cortisol released in response to?
Low
119
What does PTH cause in prolonged acidosis?
Acid secretion
120
What decreases and increases metabolic acid?
Vomiting decreases, HCO3- loss increases
121
If pH is normal what is causing the PCO2 change?
Non-respiratory causes
122
What is the ideal glomerular filtration rate?
125ml/min
123
What is normal tissue fluid osmolarity? Why is it the same in tubular fluid?
280 mosm - isotonic reabsorption
124
If low Na+ conc, what happens to the fluid at the top of the loop of Henle? What if high Na+ conc?
Just excrete the hyposmotic solution. If high, add aquaporins
125
Osmolality control is at the expense of what?
Volume control
126
What does hyponatraemia cause?
Nausea
127
Why is 200mosm the maximum gradient? What is used instead?
Fixed stoichiometry of pumps, back-leakage, instead use countercurrent multiplication
128
Is fluid from the DCT hyposmotic or hyperosmotic?
Hyposmotic
129
If conc triples, how much water is reabsorbed?
2/3
130
Where does most H2O reabsorption occur?
Cortex
131
What does heart failure cause?
Lower effective circulating volume, causing response in kidney like hypovolaemia so blood volume expands causing oedema
132
What can be used to treat heart failure?
HKCC2 or KCC blocker
133
Where does urea diffuse from and to?
Collecting duct > thin ascending limb
134
What does high medullary urea allow?
Water reabsorption from descending limb so NaCl because concentrated and can be passively absorbed
135
What does countercurrent exchange avoid?
Filling medulla with water, balanced by vasa recta
136
What are the three stimuli to thirst?
High plasma osmotic pressure, reduced extracellular fluid volume, dry throat
137
What is osmotic thirst due to?
High osmotic pressure detected by less sensitive hypothalamic osmoreceptors in the OVLT
138
What is hypovolaemic thirst due to?
Reduced extracellular volume detected by arterial and cardiopulmonary stretch receptors - inputs inhibit thirst centres and angiotensin stimulates thirst in hypovolaemia
139
What are the two types of diabetes insipidus?
Nephrogenic (failure to respond to ADH) or neurogenic (failure to produce ADH)
140
How do you treat neurogenic diabetes insipidus?
Fake ADH called desmopressin acetate
141
What determines the volume of the ECF? Why?
[Na+] because volume = amount/conc
142
Why does increase filtration fraction mean more is reabsorbed?
Peritubular capillary collid osmotic pressure raised and hydrostatic pressure lowered, Na+/fluid reabsorbed because renal interstitial hydrostatic pressure falls
143
How does extracellular fluid expansion increase ABP which increases Na+ excretion?
Higher ABP means higher net filtration rate and GFR, more filtered and less reabsorbed so more lost in urine, pressure natriuresis because water follows so decreased extracellular fluid volume, increased colloid osmotic pressure increases Na+ excretion
144
What modulates activity of renal sympathetic nerves?
Inputs from cardiopulmonary receptors and arterial baroreceptors (reduced volume/ABP inhibits sympathetic outflow less)
145
What does NA to alpha1 receptors on PCT do?
Increase NHE3 activity so more Na+ reabsorbed
146
Which hormones affect Na+ excretion?
Angiotensin II, aldosterone, ANP
147
Where is angiotensinogen always present?
Blood
148
Where is renin released from?
Juxtaglomerular cells
149
When is renin relased?
If ABP decreases - either detected by afferent arteriole or decreases cardiopulmonary and arterial stretch > sympathetic nerves > NA > beta1 > renin release
150
What does macula densa sense and what does it do about it?
Detects low NaCl, increases renin release using prostaglandin
151
What does angiotensin promote secretion of?
Renin as more NaCl reabsorbed (+ve feedback)
152
What does selective efferent constriction ensure?
Some filtration remains to remove waste products
153
Which exchanger does angiotensin stimulate and what does this cause?
Na+/H+ exchanger, increases Na+ reabsorption
154
What 4 things does angiotensin II do?
Increases Na+ reabsorption, constricts efferent arteriole, stimulates Na+ appetite, stimulates aldosterone release
155
What does aldosterone act on?
Cortical collecting duct
156
What does aldosterone promote?
Na+ reabsorption, K+ secretion and excretion and H+ excretion
157
What does aldosterone act as a transcription factor for?
Three genes (aldosterone induced proteins)
158
What does aldosterone do in principal cells?
Increased Na+ channel to stimulate Na+/K+ channel and increased Ca2+-activated K+ channel by DNA. Upregulates SK and ENaC
159
What does aldosterone do in type A intercalated cell?
Increases K+/H+ exchanger (non-genomic effect)
160
What are the stimuli to release aldosterone?
AII, increased plasma [K+], decreased plasma [Na+]
161
What is aldosterone deficiency?
Addison's disease
162
What symptoms does aldosterone deficiency cause?
Reduced plasma volume, circulatory collapse, deregulation of extracellular K+
163
What does aldosterone excess cause?
Conn's disease?
164
What are symptoms of excess aldosterone?
High ABP, high ECF, K+ depletion, alkalosis because exchanged with H+
165
How does MSP drop cause renin release?
Detected by low-pressure baroreceptors > brain stem > renal sympathetic nerve > granule cells > NA > renin release
166
ECF expansion has opposite effect to haemorrhage EXCEPT WHAT?
ANP secretion increased
167
What happens during low volume?
Lower MSP > decreased renal blood pressure > GFR > less NaCl in filtrate
168
What are the seven role of angiotensin?
Peripheral vasoconstrictor, dipsogen, simulates Na+ hunger, increase NHE in PC, constrict efferent, causes aldosterone release
169
What secretes ANP?
Atrial myocytes during increased atrial stretch
170
What does ANP cause?
Opposite to aldosterone and AII. Has natriuretic effect so it increases Na+ loss and decreases ECF volume
171
How does ANP work?
Increases cGMP > PKG > decreased ENaC and Na+/K+ATPase
172
What does ANP inhibit secretion of?
Renin, aldosterone, ADH
173
Why does ANP cause dopamine release?
Slows Na+/K+ATPase so less solutes reabsorbed and isotonic fluid excreted
174
What does ADH do to the afferent arteriole? WHY?
Dilates it for pressure natriuresis
175
Why does ANP dilate mesangial cells?
Increases filtration surface area so increases GFR
176
What can hypocalaemia cause?
Spontaneous action potentials because threshold is decreased and -ve charge on glycoproteins isn't bound which mimics depolarisation, motor nerves susceptible so can cause contraction of larynx muscles, prolonged QT interval, tetany of respiratory muscles
177
What can hypercalaemia cause?
Increased threshold for action potentials, phosphates may precipitate causing kidney stones, muscle weakness
178
WHich two hormones are hypercalcaemic?
PTH and 1,25-DHCC
179
Which hormone is hypocalcaemic?
Calcitonin
180
Where is the non-free calcium in the blood found?
Bound to proteins or complexed with anions
181
What secretes PTH?
Chief cells of the four parathyroid glands
182
What does PTH do?
Raises Ca2+, lowers PO4 2-
183
What does PTH act on?
Bone and kidney directly,, via 1,25-DHCC in gut
184
What's the process of PTH inhibition following calcium detection?
Low-affinity GPCR receptor > PLC > DAG and IP3 > IP3 binds to EP so calcium released > PKC activated > PTH synthesis and secretion inhibited
185
What do osteoprogenitor cells differentiate into?
Osteoclasts and osteoblasts
186
Where do osteoprogenitor cells come from?
Haematopoietic stem cells
187
What do osteoblasts do?
Lay down bone, secrete collagen, secrete Ca2+ and phosphate to form matrix
188
What do osteoclasts do?
Break down bone using acid and enzymes
189
What is an osteocyte?
Mature bone cell surrounded by calcified matrix connected by cytoplasmic extensions
190
How does PTH cause rapid output of Ca2+ from bone fluid and slower mineralisation of bone?
Reduces laying down of bone by osteoblasts (stimulates them to secrete RANK-L and IL-6 which are cytokines which stimulate osteoclasts), stimulates Ca2+ uptake in osteocytes where it travels down cytoplasmic extensions and is released into ECF and interstitial fluid
191
Where is most filtered Pi reabsorbed?
PCT
192
What are the three types of Na+/Pi transporter?
IIa = 3:1, IIb = 3:1, IIc = 2:1
193
How does PTH affect phospahte reabsorption transport?
Decreases Tmax
194
How does decreasing plasma Pi cause rise in free Ca2+?
Favours calcium phosphate dissolution
195
Which kind of plasma Ca2+ is filtered?
Free
196
Where is most Ca2+ reabsorbed?
PCT
197
How is Ca2+ transported out of tubule?
NCX
198
How does most Ca2+ enter the tubule?
TRPV5/6 (channels)
199
What allows calcium shuttling from luminal to adluminal membrane?
Calbindin-D
200
Why can Ca2+ movement be regulated in the DCT and CD?
Movement here is transcellular not paracellular
201
How does PTH affect calcium reabsorption in the PCT?
Decreases it
202
What does PTH phosphorylate to increased calcium reabsorption?
NCX
203
How is the type IIa transporter controlled?
PTH produces PKA and PKC which phosphorylate NHERF-1 so it dissociates from the transporter which is then available for endocytosis
204
What does a thyroparathyroidectomy cause?
Lowered ability to recover from hypo/hypercalcaemia
205
What is the pathway of 1,25-DHCC production from cholesterol?
Cholesterol > vitamin D3 > 25-HCC > 1,25-DHCC or 24,25-DHCC
206
Where does vitamin D3 > 25-HCC?
Liver
207
Where does 25-HCC > 1,25-DHCC or 24,25-DHCC?
Kidney
208
What stimulates and inhibits 25-HCC > 1,25-DHCC?
Ca2+ inhibits, PTH, growth hormone and prolactin stimulate
209
What stimulates and inhibits 25-HCC > 24,25-DHCC?
Ca2+ stimulates, PTH, growth hormone and prolactin inhibits
210
What does 1,25-DHCC do?
Increases calcium and phosphorus reabsorption in kidney and increases absorption in the small intestine enabling bone mineralisation
211
What is a synergist of 1,25-DHCC?
PTH
212
What happens if there's inadequate 1,25-DHCC?
Abnormal bone mineralisation
213
How does 1,25-DHCC work?
Increases TRPV5/6 and calbindin-D in DCT, CD and small intestine, increases type II Na+/Pi absorbers and type III in the small intestine
214
What secretes calcitonin?
C cells of the thyroid gland
215
What does calcitonin do?
Inhibits absorption of bone by osteoclasts so bone deposition favoured
216
How does calcitonin work?
Ca2+ acts on receptor, forms IP3, Ca2+ increases stimulating calcitonin (feed-forward)
217
What GI hormone stimulates calcium release?
Gastrin
218
What are the renal effects of calcitonin?
None
219
How does calcitonin protect maternal bone against excessive demineralisation?
Ensures demand met by gut absorption, sex steroids stimulate production so after menopause there's increased osteoclast activity so bone demineralisation
220
What problem with the thyroid causes hypercalcaemia? Hypocalcaemia?
Hyperparathyroidism, hypoparathyroidism
221
What causes milk fever?
Insensitivity to PTH
222
What happens in PTH excess?
Ca2+ excretion increases due to increased filtered load
223
What is the reversal potential?
Eqm potential
224
What is nAChR permeable to?
Sodium in and potassium out
225
Where are positive charges on channel which cause rotation and opening?
S4 section
226
What is K channel blocker?
Tetraethylammonium
227
What is Na channel blocker?
TTX
228
What is NaKATPase blocker?
Digitalis and ouabain
229
What is the descending limb permeable to?
Water
230
What is the thin ascending limb permeable to?
Solute passively
231
What is the thick ascending limb permeable to?
Solute actively
232
What do osmorecetors detect is isotonic fluid or haemorrhage?
No change
233
What does the pneumotaxic centre do?
Inspiratory cutoff
234
What does the apneustic centre do?
Drive inspiration, phrenic nerve
235
Another name for the CPG?
Pre-Botzinger complex
236
Where is NHE found and what does it do?
Proximal tubule, for ion and water reabsorption (makes tubule acidic and cell alkaline)
237
Where is bicarb transporter found and what does it do?
Early proximal tubule for ion and water reabsorption
238
What is the difference between SGLT-1 and SGLT-2?
SGLT-1 is for late proximal tubule and and is for 2Na+, SGLT-2 is for early proximal tubule and is for one Na
239
Where is the anion-Cl- transporter and what is it for?
Late proximal tubule for ion reabsorption
240
Where is KCC transporter and what is it for?
Late proximal tubule, for ion reabsorption, unregulated K+ absorption, active NaCl transport, water reabsorption
241
Where is the NKCC2 transporter and what does it do?
Think ascending limb, for unregulated K+ reabsorption, active NaCl transport, water reabsorption
242
Why is NKCC2 energetically favourable?
Low intracellular NaCl conc
243
Where is SK found and what is it for?
Distal tubule and collecting duct, regulating K+ secretion
244
Where is NHE3 found and what does it do?
Proximal tubule and ascending limb, for bicarb reabsorption and ammoniagenesis
245
What stimulates NHE3?
Sympathetic nerves and angiotensin
246
Where is NBC1 and what does it do?
Proximal tubule and ascending limb, for bicarb reabsorption and ammoniagenesis
247
Where is Cl-/bicarb exchanger and what is it for?
Type A intercalated cell of collecting duct for bicarb reabsorption, ammonia trapping and ammoniagenesis
248
Where is K+-H+ATPase found and what is it for?
Collecting duct for ammonia trapping
249
Where is H+-ATPase and what is it for?
Collecting duct, for ammonia trapping (makes lumen acidic)
