Renal Regulation of Water and Acid-Base Balance Flashcards
Equation for osmolarity
concentration x no of dissociated particles
units Osm/L or mOsm/l
List examples of unregulated water loss.
sweat
faeces
vomit
water evaporating from resp lining and skin
List an example of regulated water loss.
urine production
What percentage of water is reabsorbed in the proximal convoluted tubule?
67%
What condition is required for water to be reabsorbed into the loop of Henle and collecting duct?
medullary interstitium must be hyperosmotic to provide a gradient
By what mechanism does the loop of Henle concentrate urine?
countercurrent multiplication
urea recycling
SLIDE
Amino acid length of ADH
9
another name for ADH?
vasopressin
main function of ADH
promote water reabsorption from collecting duct
where is ADH produced?
hypothalamus
neurons in supraoptic and paraventricular nuclei
where is ADH stored?
posterior pituitary
how are changes in plasma osmolarity detected?
osmoreceptors in hypothalamus
normal plasma osmolarity in a healthy adult?
275-290 mOsm/kg
What % change is required for detection by baroreceptors?
5-10
stimulatory factors that influence ADH production and release
^ plasma osmolarity decreased BP hypovolaemia nausea angiotensin II nicotine
inhibitory factors that influence ADH production and release
decreased plasma osmolarity hypervolemia ^ BP ethanol atrial natruiretic peptide
mechanism of action of ADH
ADH acts on a G-protein coupled receptor > (adenylate cyclase > cAMP > pkA) > ^transcription + insertion Aquaporin–2 channels to apical membrane of the DCT + CD > ^ permeability to water > water moves out of nephron > into blood stream
list examples of ADH-related clinical disorders
central diabetes insipidus
nephrogenic diabetes insipidus
syndrome of inappropriate ADH secretion
cause of central diabetes insipidus
decreased/negligent production and release of ADH
clinical features of central diabetes insipidus
polyuria
polydipsia
treatment for central diabetes insipidus
external ADH
cause for SIADH
increased production and release of ADH
clinical features of SIADH
hyperosmolar urine
hypervolemia
hyponatremia
treatment for SIADH
non-peptide inhibitor of ADH receptor (conivaptan & tolvaptan)
cause of nephrogenic diabetes insipidus
less/mutant AQP2
mutant V2 receptor
symptoms of nephrogenic diabetes insipidus
polyuria
polydipsia
treatment for nephrogenic diabtes insipidus
thiazide diuretics and NSAIDs
role of kidneys in acid base balance
secretion and excretion of H+
reabsorption of HCO3-
production of new HCO3-
what enzyme catalyses the reaction between CO2 and H20?
carbonic anhydrase
majority of HCO3- is reabsorbed where?
PCT
how is HCO3- reabsorbed in PCT?
CO2 diffuses in > catalysed by carbonic anhydrase with H20 > H+ + HCO3- > via NA+ - HCO3- symporter to blood stream
function of alpha intercalated cell
HCO3- reabsorption & H+ secretion
function of beta intercalated cell
HCO3- secretion & H+ reabsorption
production of NEW bicarbonate ion in the PCT
glutamine broken down into 2NH4+ and A2- > A2- to 2HCO3- > absorbed into blood
NH4+ removed via Na+ antiporter or NH3 removed over membrane and H+ via Na+ antiporter
production of NEW bicarbonate ion in the DCT + CD
in alpha intercalated cell
water + CO2 > H+ + HCO3- > transported via Cl- - HCO3- antiporter
characteristics of metabolic acidosis
decreased HCO3-
decreased pH
characteristics of metabolic alkalosis
increased HCO3-
increased pH
characteristics of respiratory acidosis
increased pCO2
decreased pH
characteristics of respiratory alkalosis
decreased pCO2
increased pH
compensatory response for metabolic acidosis
increased ventilation to blow off CO2
^ [HCO3-] reabsorption and production
compensatory response for metabolic alkalosis
decreased ventilation
^ [HCO3-] excretion
compensatory response for acute respiratory acidosis
intracellular buffering
compensatory response for chronic respiratory acidosis
^ [HCO3-] reabsorption and production
compensatory response for acute respiratory alkalosis
intracellular buffering
compensatory response for chronic respiratory alkalosis
decreased [HCO3-] reabsorption and production