Tubular Transport - McCormick Flashcards
Pinocytosis
Protein reabsorption
Proximal tubule reabsorbs what?
Na+ K+ Cl- HCO3- Ca2+ Phosphate water ALL glucose, AA
TF/P ratio in Proximal tubular lumen of inulin
Starts at 1
Goes to 3 - water has left, inulin concentration stays same in less water
TF/P ratio in Proximal tubular lumen of glucose
Starts at 1
Goes to 0 - all of the glucose has been reabsorbed
TF/P ratio in Proximal tubular lumen of PAH
Starts at 1
Goes to 10 - PAH is secreted
Transporters in the proximal tubule
Na - Glucose
Na+ - H+
Transporter in the PT interstitium
Na-K ATPase
Transporter on the loop
Na-K-2Cl
As water and Na+ are reabsorbed, what happens to Cl- and urea in PCT?
Become more concentrated in the lumen fluid
-provides driving force for paracellular reabsorption
2 factors promoting fluid movement into peritubular capillaries?
High plasma colloid osmotic pressure
Low hydrostatic pressure in these capillaries
What regulates plasma concentrations of glucose and AA?
Liver and endocrine system
-secondary active transport, transcellular only
Mechanism of glucose reabsorption
Coupled reabsorption of Na+ and glucose in PT
Na-glucose cotransport
Facilitated diffusion
Glucosuria
Glucose in urine
Capacity of transporters saturated
-same idea applies to AA
Tmg
Tubular glucose maximum
-rate of glucose reabsorption by all nephrons combined
2 consequences of osmotic diuretics
Increased water excretion
Increased sodium excretion
Secretion of organic ions
PAH, bile salts, uric acid, creatinine
Tertiary active transport
ALSO drugs like PCN, salicylates
Is PAH secretion saturable?
Yes
Charged organic acids and bases
Highly polar
Cannot readily diffuse through lipid bilayer
Uncharged organic acids and bases
Less polar, more lipid soluble
Therefore can go across membrane
Weak acids are neutral when
Protonated
-H+ is added
Weak bases are neutral when
Deprotonated
-H+ taken away
H+ in the tubular lumen favors
Reabsorption of organic acids, but traps organic bases int he lumen
Osmotic diuretics increase?
H2O, Na+ excretion
Organic nutrients
Reabsorbed by secondary active transport
Linked to Na+ reabsorption
