PHYSIOLOGY OF CONNECTING TUBULE AND COLLECTING DUCT

1. PHYSIOLOGY OF CONNECTING TUBULE AND
COLLECTING DUCT

2. From: Chapter 277. Cellular and Molecular Biology of the Kidney
Harrison's Principles of Internal Medicine, 18e, 2012

4. Figure 1 Pathways of steroid biosynthesis in the adrenal cortex
White, P. C. (2009) Neonatal screening for congenital adrenal hyperplasia
Nat. Rev. Endocrinol. doi:10.1038/nrendo.2009.148

6. From: Chapter 277. Cellular and Molecular Biology of the Kidney
Harrison's Principles of Internal Medicine, 18e, 2012
Proteolytic processing steps in the generation of angiotensins.
Date of download: 5/14/2014 Copyright © 2012 McGraw-Hill Medical. All rights reserved.

10. From: Chapter 277. Cellular and Molecular Biology of the Kidney
Harrison's Principles of Internal Medicine, 18e, 2012
Date of download: 5/14/2014 Copyright © 2012 McGraw-Hill Medical. All rights reserved.

11. From: Chapter 277. Cellular and Molecular Biology of the Kidney
Harrison's Principles of Internal Medicine, 18e, 2012
Date of download: 5/14/2014 Copyright © 2012 McGraw-Hill Medical. All rights reserved.

21. Effects of aldosterone
-- Latent
-- Early
-- Late

26. POTASSIUM

27. • The potassium channels
-ROMK
-BK

29. Structure and distribution of ROMK channels.
(A) Schematic presentation of ROMK structure
shows two characteristic transmembrane
segments (TM1 and TM2; blue and green,
respectively), NH2- and COOH-termini and an
extracellular domain. (B) Predicted structure of
ROMK subunit stoichiometry. (C) Distribution
of ROMK isoforms expression along the
nephron. TAL, thick ascending limb of Henle’s
loop; DCT, distal convoluted tubule; CNT,
connecting tubule; CCD, cortical collecting
duct; OMCD, outer medullary collecting duct.

30. The structure of the pore-forming α-subunit and regulatory β-
subunit of the BK channel (A). α-subunit contains 7 putative
transmembrane domains, S0–S6, a conserved K+-selective pore
region between S5 and S6, and a long COOH-terminal cytosolic
tail. β-subunit contains two transmembrane segments and
short NH2- and COOH-termini. (B) Proposed model of BK
channel. Four BK α-subunits co-assemble with four BK β-
subunits to form the channel heteromultimer.

36. TRPVs

37. Transmembrane topology of TRP channels. TRP channels
belong to the large superfamily of cation channels with six
transmembrane-spanning segments forming a transmembrane
domain with a pore loop inserted between TM5 and TM6 and
NH2- and COOH-intracellular termini (A). In contrast, polycystin
1 (PKD1 or PC1) has eleven transmembrane domains and a
large extracellular NH2 domain (B).

38. Modes of transepithelial transport and major proteins
involved in the paracellular transport. Schemes of the
transcellular (A) and paracellular (B) epithelial transport.
(C) Schematic three-dimensional structure of tight
junctions. Proposed structures of claudin (D) and occludin
(E).

39. ACID BASE BALANCE

43. Scheme of the V-type H+-ATPase. H+-ATPases use the energy
released by the hydrolysis of ATP to move protons against their
concentration gradients. The V0 domain is involved in
translocation of the protein. The V1 domain is involved in ATP-hydrolysis.
The precise subunits composition is not entirely
clear and several slightly different schemes are proposed. For
details see recent excellent reviews providing details about
subunits and domains of V-type H+-ATPase

44. Proposed schematics of Cl−/HCO3
− exchangers. The
structures of anion exchanger AE1 (SLC4A1) (A) and
pendrin (SLC26A4) (B) are shown. As seen from these
schemes, both NH2- and COOH-termini of AE1 are
intracellular. In contrast, COOH-terminus of pendrin is
extracellular

46. Expression patterns of sodium and potassium transport systems and of their regulatory proteins along the distal
convoluted tubule (DCT), connecting tubule (CNT), and cortical collecting duct (CCD).
Meneton P et al. Am J Physiol Renal Physiol 2004;287:F593-F601
©2004 by American Physiological Society

47. Apical localization of ENaC and ROMK in the renal distal tubule and collecting system.
Meneton P et al. Am J Physiol Renal Physiol 2004;287:F593-F601
©2004 by American Physiological Society

48. 1. Water and kidney

49. Water and kidney
• 180 liters/day of fluid filtered
• 162 liter reabsorbed in the proximal tubule and loop of Henle
• Most of remaining 18 liters reabsorbed in collecting duct
Rector and Brenner’s the Kidney 9th ed. (2012)

50. Water and kidney
Medullary osmotic
gradient
Hyperosmotic medullary
interstitium
UpToDate

51. Urea recycling
• Key to maintain the concentrating
mechanism
• Urea transporters
• UTA1, 3 in IMCD*
• UTA2 in TAL*
• UTB in vasa recta
*regulated by AVP
JASN 2007 18 679

52. AQPs in the nephron
Physiol Rev 2002 82 205

53. Regulation of the aquaporin-2 (AQP2)-mediated
water transport by arginine vasopressin (AVP). (A)
Proposed topology of AQP2. An AQP2 monomer
consists of six transmembrane domains
connected by five loops. NH2- and COOH-termini
are located intracellularly. (B) A scheme of water
transport regulation by AVP. Vasopressin receptor
(V2R), stimulatory GTP-binding protein (Gs),
adenylate cyclase (AC), adenosine triphosphate
(ATP), and cyclic adenosine monophosphate
(cAMP) are indicated.

54. From: Chapter 277. Cellular and Molecular Biology of the Kidney
Harrison's Principles of Internal Medicine, 18e, 2012
Determinants of sodium and water balance. A. Plasma Na+ concentration is a surrogate marker for plasma tonicity, the volume behavior of cells in a solution. Tonicity is determined by the number of effective
osmols in the body divided by the total body H2O (TB H2O), which translates simply into the total body Na (TB Na+) and anions outside the cell separated from the total body K (TB K+) inside the cell by the cell
membrane. Net water balance is determined by the integrated functions of thirst, osmoreception, Na reabsorption, vasopressin release, and the strength of the medullary gradient in the kidney, keeping tonicity
within a narrow range of osmolality around 280 mosmol/L. When water metabolism is disturbed and total body water increases, hyponatremia, hypotonicity, and water intoxication occur; when total body water
decreases, hypernatremia, hypertonicity, and dehydration occur. B. Extracellular blood volume and pressure are an integrated function of total body Na+ (TB Na+), total body H2O (TB H2O), vascular tone, heart
rate, and stroke volume that modulates volume and pressure in the vascular tree of the body. This extracellular blood volume is determined by net Na balance under the control of taste, baroreception, habit, Na+
reabsorption, macula densa/tubuloglomerular feedback, and natriuretic peptides. When Na+ metabolism is disturbed and total body Na+ increases, edema occurs; when total body Na+ is decreased, volume
depletion occurs. ADH, antidiuretic hormone; AQP2, aquaporin-2.

55. From: Chapter 277. Cellular and Molecular Biology of the Kidney
Harrison's Principles of Internal Medicine, 18e, 2012
Determinants of sodium and water balance. A. Plasma Na+ concentration is a surrogate marker for plasma tonicity, the volume behavior of cells in a solution. Tonicity is determined by the number of effective
osmols in the body divided by the total body H2O (TB H2O), which translates simply into the total body Na (TB Na+) and anions outside the cell separated from the total body K (TB K+) inside the cell by the cell
membrane. Net water balance is determined by the integrated functions of thirst, osmoreception, Na reabsorption, vasopressin release, and the strength of the medullary gradient in the kidney, keeping tonicity
within a narrow range of osmolality around 280 mosmol/L. When water metabolism is disturbed and total body water increases, hyponatremia, hypotonicity, and water intoxication occur; when total body water
decreases, hypernatremia, hypertonicity, and dehydration occur. B. Extracellular blood volume and pressure are an integrated function of total body Na+ (TB Na+), total body H2O (TB H2O), vascular tone, heart
rate, and stroke volume that modulates volume and pressure in the vascular tree of the body. This extracellular blood volume is determined by net Na balance under the control of taste, baroreception, habit, Na+
reabsorption, macula densa/tubuloglomerular feedback, and natriuretic peptides. When Na+ metabolism is disturbed and total body Na+ increases, edema occurs; when total body Na+ is decreased, volume
depletion occurs. ADH, antidiuretic hormone; AQP2, aquaporin-2.

56. Free water excretion
• 2 determinants
A. Solute load
B. Degree of antidiuresis
Effects of ADH on urine volume in a subject excreting 800mOsm
of solute per day
ADH Uosm UV (L/day)
0 80 10
++ 400 2
+++ 1200 0.67
Clinical physiology of acid-base and electrolyte disorder 5th ed. (2001)

57. Free water excretion
• Free water clearance (CH2O)
*
*
for electrolyte-free water clearance
JASN 2008 19 1076
Positive CH2O = kidney is excreting water
Negative CH2O = kidney is conserving water

58. Free water excretion
Elderly patients
• Decreased max. urine concentration (500-700 mOsm/kg)
SIADH
• Impaired max. urinary dilution  water retention
Primary polydipsia
• Water intake > water excretion
Rector and Brenner’s the Kidney 9th ed. (2012)

59. Nitrogen excretion
Ammonia
Journal of Experimental Biology 1995 198 273
Urea Uric acid
Too toxic for terrestrial animals
(400ml of water to dilute 1g of ammonia
below toxic level)
Saves water ~ 10x more than ammonia to
excrete
Saves water ~ 50x more than ammonia to
excrete

60. Part 1: Summary
Water absorption
• loop of Henle (AQP1)
• collecting duct (AQP2)  AVP
 Osmotic gradient
• countercurrent multiplier
• urea recycling  AVP
 Free water excretion
• (effective) solute load
• antidiuresis

61. 2. Regulation of AVP

62. Stimuli of AVP secretion
A. Osmolarity ↑
B. Volume loss
C. Others
• Nausea
• Angiotensin II
• Stress
• Hypoxia
• Drugs, etc.
Acetylcholine Cyclophosphamide*
Nicotine Vincristine
Apomorphine Insulin
Morphine 2-deoxyglucose
Epinephrine Lithium
Isoproterenol Naloxone
Histamine Cholecystokinin
Bradykinin Beta-endorphin
Prostaglandin (*intravenous)
Rector and Brenner’s the Kidney 9th ed. (2012)

63. Inhibitors of AVP secretion
A. Osmolarity ↓
B. Hypervolemia
C. Others
• Drinking
• Drugs, etc.
Norepinephrine Carbamazepine
Fluphenazine Glucocortisoids
Haloperidol Clonidine
Promethazine Muscimol
Oxilophan Phencyclidine
Butorphanol Phenytoin
Opioid agonists Ethanol
Demeclocycline? ( ↓ responsiveness to AVP)
Vaptans? (blocks V2R)
Rector and Brenner’s the Kidney 9th ed. (2012)

64. Osmoreceptor
• OVLT (organum vasculosum of the lamina terminalis)
• Lacking BBB
• Depolarizes with shrinkage* (sensing osmolarity ↑)
Osmoreceptor dysfunction
• Adipsic hypernatremia ↔ dipsogenic DI
• Brain lesion (A-comm. aneurysm), etc.
Rector *TRPVs may be responsible and Brenner’s the Kidney 9th ed. (2012)

65. Neural network & AVP
Anterior Hypothalamus
Ascending brainstem pathways
Rector and Brenner’s the Kidney 9th ed. (2012)

66. Osmolarity & AVP secretion
Rector and Brenner’s the Kidney 9th ed. (2012)

67. Baroreceptors

68. Osmolarity vs. Volume
Fine tuning
(minute-to-minute)
For emergency
(large volume loss)
Rector and Brenner’s the Kidney 9th ed. (2012)

69. Osmolarity + Volume
VOLUME
WINS!
Rector and Brenner’s the Kidney 9th ed. (2012)

70. Nausea
• Super-potent stimuli*
• Hundreds pg/ml!
• Reversed by antiemetics
KI 1979 16 729

71. Thirst
• Most drinking is not from “true thirst”
• Higher osmotic threshold
• Freeing human from frequent episodes of thirst
Rector and Brenner’s the Kidney 9th ed. (2012)

72. Part 2: Summary
 AVP stimuli
• high osmolarity (OLVT in anterior hypothalamus)
• low volume (baroreceptors)
• others
 Fine tuning by osmolarity
 Emergency call by volume
 Thirst: back-up system

73. 3. AVP  V2R  AQP2

74. Arginine vasopressin (AVP)
• ADH = AVP
• 9 amino acids
• Highly conserved across species
Rector and Brenner’s the Kidney 9th ed. (2012)

75. Vasopressin superfamilies
Cys-Tyr-Phe-Gln-Asn-Cys-Pro-Arg-Gly-NH2
Cys-Tyr-Phe-Gln-Asn-Cys-Pro-Lys-Gly-NH2
Cys-Phe-Phe-Gln-Asn-Cys-Pro-Arg-Gly-NH2
Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Arg-Gly-NH2
Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly-NH2
Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Pro-Gly-NH2
Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Ile-Gly-NH2
Cys-Tyr-Ile-Gln-Ser-Cys-Pro-Ile-Gly-NH2
Cys-Tyr-Ile-Ser-Asn-Cys-Pro-Ile-Gly-NH2
Cys-Tyr-Ile-Ser-Asn-Cys-Pro-Gln-Gly-NH2
Cys-Tyr-Ile-Asn/Gln-Asn-Cys-Pro-Leu/Val-Gly-NH2
Cys-Leu-Ile-Thr-Asn-Cys-Pro-Arg-Gly-NH2
Cys-Phe-Val-Arg-Asn-Cys-Pro-Thr-Gly-NH2
Cys-Phe-Ile-Arg-Asn-Cys-Pro-Lys-Gly-NH2
Cys-Ile-Ile-Arg-Asn-Cys-Pro-Arg-Gly-NH2
Cys-Tyr-Phe-Arg-Asn-Cys-Pro-Ile-Gly-NH2
Cys-Phe-Trp-Thr-Ser-Cys-Pro-Ile-Gly-NH2
AVP
Vasotocin (prototype)
Oxytocin
Sharks
Locust (diuretic hormone)
Snail
Octopus
Wikipedia “vasopressin”

76. Arginine vasopressin (AVP)
• Chromosome 20
• 3 exons, 145 amino acids
Rector and Brenner’s the Kidney 9th ed. (2012)

77. Arginine vasopressin (AVP)
Congenital CDI
• All autosomal dominant
• Abnormal precursor protein accumulates and eventually kills the neuron
• Could be partial DI
Rector and Brenner’s the Kidney 9th ed. (2012)

78. Arginine vasopressin (AVP)
Destruction leads to CDI
(autoimmune process,
malignancy, trauma, hemorrhage,
etc.)
Destruction of pituitary gland
rarely causes CDI (hypothalamus
is intact)

79. Arginine vasopressin (AVP)
• Action via V1R
• Vasoconstriction
• Prostaglandin production
• Actions via V2R
• AQP2 accumulation in apical membrane (principal cells)
• Stimulate NaCl reabsorption in TAL
• Transepithelial movement of urea (terminal CD)
• release of vWF (endothelium)
Rector and Brenner’s the Kidney 9th ed. (2012)

80. Arginine vasopressin (AVP)
• Metabolism
• Short half life (10-20 minutes)
• Metabolized in liver and kidney
Increased in pregnancy
• Gestational DI
• cysteine aminopeptidase from placenta degrades both oxytocin and AVP
• suspect other underlying partial DI

81. DDAVP
• De-aminated 1Cys, Dexter 8Arg
• V2R specific agonist
• Longer half life (up to 3 hrs*)
de-aminated
dexter
*9 hrs in renal failure

82. AVP  V2R  AQP2
Eur J Physiol 2012 464 133

83. V2R
• G protein-coupled receptor
→ cAMP → PKA activation (S256 of AQP2)
X-linked NDI (90% of congenital NDI)
• Dysfunctional V2R
oNot inserted to the membrane
oNot able to bind AVP
oNot able to activate AC
Rector and Brenner’s the Kidney 9th ed. (2012)

84. AQP2
• AQP2 = AVP-sensitive water channel
• Accumulated with AVP
• Phosphorylation (C terminal)  PKA & AKAP18σ
• Continually recycled
Autosomal recessive NDI
• AQP2 misfolding  retention in ER  degraded
Autosomal dominant NDI (rare)
• AQP2 C terminal mutation  trafficking problem
Rector and Brenner’s the Kidney 9th ed. (2012)

85. AQP2
Lithium
• Enters through ENaC  decreases AQP2 expression (? GSK3-beta)
Hypercalcemia
• Activates CaSR in apical membrane of principal cells  decreases AQP2
expression (? mechanism)
Hypokalemia
• decreases AQP2 expression (? mechanism)

86. Part 3: Summary
 ADH = AVP
• Spliced from precursor (congenital CDI)
• Gestational DI
 V2R
• phosphorylates AQP2
• X-linked NDI (90%)
 AQP2
• continually recycled
• Autosomal recessive NDI (10%)
• Lithium, ↑Ca, ↓K

87. THANK YOU

90. • Pha2

92. Figure 2 Overview of the control of sodium transport by aldosterone. Arrows indicate the direction of the signaling cascade. AIP , aldosterone induced protein; MR , mineralocorticoid
receptor;...
Manlio Vinciguerra , David Mordasini , Alain Vandewalle , Eric Feraille
Hormonal and Nonhormonal Mechanisms of Regulation of the Na,K-Pump in Collecting Duct Principal Cells
Seminars in Nephrology, Volume 25, Issue 5, 2005, 312 - 321
http://dx.doi.org/10.1016/j.semnephrol.2005.03.006

93. Figure 1 Mechanism of sodium, potassium, and water transport in principal cells of the CD. Arrows indicate net fluxes of water and ions. The names of the currently cloned
transporters are shown in rectangular boxes.
Manlio Vinciguerra , David Mordasini , Alain Vandewalle , Eric Feraille
Hormonal and Nonhormonal Mechanisms of Regulation of the Na,K-Pump in Collecting Duct Principal Cells
Seminars in Nephrology, Volume 25, Issue 5, 2005, 312 - 321
http://dx.doi.org/10.1016/j.semnephrol.2005.03.006

94. Figure 3 Overview of the control of sodium transport by vasopressin. Arrows indicate the direction of the signaling cascade. PKAR , protein kinase A regulatory subunit, V 2
receptor.
Manlio Vinciguerra , David Mordasini , Alain Vandewalle , Eric Feraille
Hormonal and Nonhormonal Mechanisms of Regulation of the Na,K-Pump in Collecting Duct Principal Cells
Seminars in Nephrology, Volume 25, Issue 5, 2005, 312 - 321
http://dx.doi.org/10.1016/j.semnephrol.2005.03.006

95. Figure 4 Overview of the putative intracellular sodium-dependent signaling pathway controlling the recruitment of Na,K-ATPase. Arrows indicate the direction of the signaling
cascade. N , nucleus; V2</CE:SMALL...
Manlio Vinciguerra , David Mordasini , Alain Vandewalle , Eric Feraille
Hormonal and Nonhormonal Mechanisms of Regulation of the Na,K-Pump in Collecting Duct Principal Cells
Seminars in Nephrology, Volume 25, Issue 5, 2005, 312 - 321
http://dx.doi.org/10.1016/j.semnephrol.2005.03.006

96. Figure 5 Overview of the main signaling pathways controlling the active sodium and potassium transport in CD principal cells. Arrows indicate the direction of the signaling
cascade and the resulting stimulatory (+) or inhibitory (-) effect on their targets...
Manlio Vinciguerra , David Mordasini , Alain Vandewalle , Eric Feraille
Hormonal and Nonhormonal Mechanisms of Regulation of the Na,K-Pump in Collecting Duct Principal Cells
Seminars in Nephrology, Volume 25, Issue 5, 2005, 312 - 321
http://dx.doi.org/10.1016/j.semnephrol.2005.03.006

97. • Avp

101. Collecting tubule acid–base transporters involved in H+ secretion and HCO3− reabsorption by α-intercalated cells (A) and β-
intercalated cells (B).
Batlle D , and Haque S K Nephrol. Dial. Transplant. 2012;27:3691-3704
© The Author 2012. Published by Oxford University Press on behalf of ERA-EDTA.

102. Schematic model of various mechanisms, whereby kAE1 mutations result in abnormal Cl−/HCO3− in dRTA.
Batlle D , and Haque S K Nephrol. Dial. Transplant. 2012;27:3691-3704
Schematic model of various mechanisms, whereby kAE1
mutations result in abnormal Cl−/HCO− in dRTA.
3
(A) Normal, (B) internal sequestration in the endoplasmic
reticulum
(C) internal sequestration in the golgi apparatus
(D) non-functional/partially functional
(E) mistargeting to both the apical membrane and
basolateral
© The Author 2012. Published by Oxford University Press on behalf of ERA-EDTA.