Tubular Reabsorption Flashcards
Splay
Appearance of a substance in the urine before Tm is reached
*not all nephrons will express the same Tm for a substance
Glucose Reabsorption
Crosses the apical membrane via secondary transport w/ Na+; crosses the basolateral membrane via facilitated diffusion
Glucose Clearance Formula
Cg= Cin-TMg/Pg
*As Pg increases, Cg approaches Cin
Renal Glycosuria
Glucose appearance in urine due to defect in transport mechanism
Diabetes Mellitus
Glucosuria due to lack of insulin production
Tg= OK
Pregnancy glucosuria
Increased GFR due to gestational hormones
Tg=OK
B-hydroybutyrate reabsorption
Low renal threshold; kidneys regulate body concentrations
*Excretion increased in diabetes mellitus and starvation due to increased fat mobilization and utilization
Filtration of Proteins
Small due to:
Steric Hinderance
Viscous Drag
Electrical hinderance
Mechanism of Protein reabsorption
Taken into cell by pinocytosis and apical vesicles fuse w/ lysosomes; AAs released into peritubular fluid
Renal Effects of PTH
Promotes calcitriol formation
Increases Ca2+ reabsorption
Increases PO43- excretion
Ca2+ reabsorption
Proximal tubule: paracellular - moves across brush border and thru basolateral membrane via a Ca2+-ATPase
Transcellular also occurs
Thick ascending limb: Paracellular
*Distal tubule:Transcellular; Ca2+ crosses apical membrane and binds w/ Calbindin which transports it to the basolateral membrane where it moves across via Na+/Ca2+ anti porter
PO43- reabsorption
Secondary active transport @ apical membrane; Pi-anion antiporter at basolateral membrane
PTH effects on PO43-
Removes NPT2 reabsorption protein from the proximal tubule
Small peptide reabsorption
Hydrolyzed by peptidases on the luminal membrane and actively reabsorbed in to interstitium
