Session 3.3: Ion Transport in Renal Physiology Flashcards
what have transporters got to do with renal medicine
bicarbonate reabsorption of the proximal tubule - pH control
sodium re-uptake by the kidney - control of hypertension
what is the sequence of transport in the kidney
blood enters through glomerulus -> proximal tubule -> descends into kidney -> filtrate passes through loop of Henle -> passes through thick ascending limb -> distal convoluted tubule -> cortical collecting duct -> out of kidney
how does sodium and bicarbonate reuptake by kidney promixal tubule cells work
sodium potassium ATPase is driving sodium out ofthe proximal tubule cell and into the capillary. this creates a gradient so sodium flows down its concentration gradient into the proximal tubule cell via sodium/hydrogen exchange. this causes acification fo the filtrate. so then bicarbonate buffers. so HCO3- and H+ combine to form carbonic acid. carbonic anhydrase catalyses the conversion of carbonic acid into water and co2. co2 diffuses into proximal tubule cell with water and forms carbonic acid which then forms hydrogen ions and hydrogen carbonate ions. the hydrogen ions then are circulated. the bicarbonate in anion exchanger into capillary, whcih provides driving force for chloride into the cell
what is the main function of the kidney
reabsorb all the bicarbonate filtered into the proximal tubule to retain base for pH buffers
how is renal control related to medicine
if control of circulating sodium concentration is a treatment for mild hypertension
how is sodium uptake by the proximal tubule inhibited
by a drug called amiloride
if sodium hydrogen exchange blocked, sodium can no longer enter into the cell so into filtrate in urine and excreted
water follows - diuresis so less water uptake, blood volume and pressure decreases
it also blocks bicarbonate reuptake - bad effect on body buffering
how does sodium reuptake take place in thick ascending limb
sodium/potassium ATPase - gradient for sodium so allows sodium uptake by sodium/potassium/chloride transporter which can then be taken into cell and intom blood via sodium potassium ATPase
potassium/chloride co transporter and a chloride channel and voltage insensitive potassium channels - all balance ion concentrations - to allow uptake of sodium
what is the sodium/potassium/chloride transporter sensitive too
loop diuretics
reducing uptake of sodium across thick ascending limb
how does sodium reuptake occur in the distal convoluted tubule
sodium enters the cell through sodium/chloride cotransporter and into blood stream via sodium/potassium ATPase = sodium gradient
chloride and potassium leaves into blood through potassium/chloride cotransporter
also epithelium sodium channel which allows sodium to enter into distal convoluted tubule where transported into blood
what is sodium chloride co transporter sensitive to
thiazides diuretics
how to prevent mild hypertension
the diuretics that the transporters are sensitive to - stops uptake of sodium into the blood - decreasing blood volume and thus blood pressure
what is the epithelium sodium channel sensitive to
amiloride
how does sodium uptake occur in the cortical collecting duct
sodium-potassium ATPase, creates gradient for sodium to enter through epithelium sodium channels, chloride follows this sodium through chloride channel into blood stream
sodium transport is balanced by exit of potassium through ROMK channels
presence of aquaporins, water diffuses across channels into blood stream
what is ADH/vasopressin
increases transport of aquaporins to membrane and increases gene expression - facilitates uptake of water into bloodstream - important for water balance
how are the transporters controlled in cortical collecting duct
aldosterone - encourage retention of sodium, enhancing expression of proteins, so sodium uptake increases
