Reporting Status or Progress

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Daniel R. Kapusta, Ph.D. Department of
Pharmacology, LSUHSC MEB Rm 7106 568-3940
dkapus_at_lsuhsc.edu
Urine Concentration and Dilution Regulation of
Sodium and Water Balance
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Urine Concentration and Dilution
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AVP-dependent water permeability in the distal
nephron
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Aquaporin 2 mediated water reabsorption in DCT
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Countercurrent SYSTEM
1. Countercurrent flow direction anatomy 2.
Countercurrent exchange vasa recta 3.
Countercurrent multiplication tubules
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1. Countercurrent FLOW

• Hairpin configuration - anatomical
• - loops of Henle (tubules)
• - vasa recta (capillaries)
• Descending limbs close to ascending limbs
• Fluid flow in opposite directions

? TAL
? DVR
? tdloop
? AVR
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2. Countercurrent EXCHANGER

• Vasa recta (capillaries)
• - Countercurrent exchangers
• - Passive process depends on diffusion of
  solutes water in both directions across
  permeable walls of the vasa recta

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3. Countercurrent MULTIPLIER
Loops of Henle (tubules) countercurrent
multipliers - Pumping solute creates a large
axial gradient - Establishes hyperosmotic
medullary interstitial fluid
ISF Osmotic gradient
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Segmental renal tubular sodium reabsorption
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Recycling of urea in the kidney
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Renal handling of water in states of water
diuresis
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Renal handling of water in states of antidiuresis
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Renal handling of water in states of water
diuresis and antidiuresis
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Vasopressin Pathologies
SIADH Syndrome of inappropriate secretion of
ADH Central diabetes insipidus Nephrogenic
diabetes insipidus
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Regulation of Sodium and Water Balance
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Distribution of Total Body Water (TBW)
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Total Body Water Balance Input Output
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Total Body Sodium Balance Input Output
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Regulation of Arterial Blood Pressure
BP CO x TPR
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Regulation of Arterial Blood Pressure
BP CO x TPR
HR x SV
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Regulation of Arterial Blood Pressure
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Volume and Sodium/Osmole Sensors
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Volume and Sodium/Osmole Sensors
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Regulation of Arterial Blood Pressure Closed
loop system
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Regulation of Arterial Blood Pressure and Total
Body Water / Sodium Balance
Neural Control
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Neural Control Mechanisms Baroreceptors
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Sympathetic control mechanisms regulating arterial
blood pressure and sodium/water excretion
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Renal sympathetic nerves and kidney function
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Renal nerves contribute to segmental renal
tubular sodium reabsorption
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Renal nerves innervate the afferent renal
arterioles ?1 receptor activation renin
release ?1 adrenoceptor activation
vasoconstriction
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Reduction in arterial blood volume activates the
renal sympathetic nerves to enhance renal
tubular sodium reabsorption
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Regulation of Arterial Blood Pressure and Total
Body Water / Sodium Balance
Humoral Control
- Angiotensin II
- Aldosterone
- Atrial Natriuretic Peptide (ANP)
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The renin-angiotensin-aldosterone system
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Angiotensin II
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Regulation of extracellular fluid volume
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Angiotensin II and renovascular hypertension
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Angiotensin and aldosterone enhance the renal
tubular reabsorption of sodium
? UNaV
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Chronic high salt diet reduces plasma renin (and
Ang II) and increases plasma atrial natriuretic
peptide levels
High NaCl intake
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Volume expansion Integration of neural and
humoral pathways to augment sodium and water
excretion
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Volume contraction Integration of neural and
humoral pathways to reduce sodium and water
excretion
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Deranged neural and humoral control in
hypertension
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Deranged neural and humoral control in congestive
heart failure
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Regulation of Arterial Blood Pressure and Total
Body Water / Sodium Balance
Humoral Control
AVP ADH
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Hypothalamic control of vasopressin
(antidiuretic hormone) secretion
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ADH secretion is more sensitive to
changes in plasma osmolarity than to changes in
blood volume
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At plasma AVP levels that evoke thirst, water
reabsorption and urine osmolality are already
maximally increased
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Central osmoreceptors and AVP secretion
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Major Causes of Hyponatremia and Hypo-osmolality
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Major Causes of Hypernatremia