D2O

THO

mannitol

sulfate

inulin

NO MARKER (TBW-ECF)

radioiodinated serum albumin (RISA)

Evan's blue dye

albumin (can't be filtered) and glucose (filtered, but all of it is reabsorbed) should be 0 mL/min

range = 0-600 mL/min

not metabolized

easily filtered

not reabsorbed, secreted into tumor

small

Substance whose renal clearance equal to renal plasma flow

inulin

Clearance ratio = Cx/Cinulin

Cinulin = 120 mL/min

• if =1, substance x is glomerular marker
• if <1, x is either not freely filtered or it is filtered and absorbed
• if >1, x is filtered and secreted

• creatinine secreted in PCT (overestimate urine concentration of creatinine)
• substances in blood cause overestimation of plasma creatinine (produce endogenously)

But, they both nearly cancel each other out

Creatinine concentration = (urine creatinine x urine flow)/Plasma creatinine ~ GFR

• inverse relationship
• but not a perfect relationship
  • if you decrease GFR 25%, you should increase plasma creatinine four fold, but this willl not happen
  • this does not happen because there is a compensatory increase in PCT secretion

• freely filtered
• avidly secreted in PCT
• completely cleared from peritubular capillaries when plasma PAH is low

clearance of PAH = (urine conc. of PAH x urine flow)/ plasma conc. of PAH

ONLY WORKS AT LOW CONCENTRATIONS (BELOW TRANSPORT MAXUM)

Equation for filtration fraction? average value

filtration fraction = GFR/RPF

normally, 20%

1. cotransported with Na into PCT cell (provides gradient for Na/K pump- secondary active transport)
2. sent out via glucose transporter

Daily filtered sodium

25,200 (remember clearance equation to find answer)

Different mechanisms of reabsorption

• paracellular reabsorpiton (get through tight junctions)
• transcellular reabsoption (transcellular via transporters)

Fate of H20 and CO2 in PCT cell

Remember, contains carbonic anhydrase.

• make carbonic acid
• split into bicarbonate and H
  • bicarbonate reabsorbed into blood
  • H and HCO3 can go into urine and become carbonic acid

• Acetozolamide
• Chlorothiazide
• Furosimide
• Penicillin
• Probenecid
• Salicylate (aspirin)
• HCT
• bumetanide

• cAMP
• bile salts
• hipporates
• oxalate
• PG's
• urate

• creatinine
• dopamine
• epinepherine
• norepi

atropine

isoproterenol

cimetidine

morphine

quinine

amiloride

procainamide

• Na/H cotransport into cell
• Cl/formate antiport (Cl into cell, formate into lumen)
• Na/K pump at blood/cell interface
• Cl channel at blood interface

• Na/K/2Cl transported into cell
  • establishes gradient (if you lose it, you cant eliminate water)
• Na/K pump
• K/Cl cotransport into blood
• K channel (into lumen of urin)
  • via positive potential of Mg, Ca that move via paracellular transport into blood

Site of Na/K/2Cl transporter

macula densa

thick ascending limb

• if ADH, we have aquaporins
• Na/Cl symport into cell from lumen (block via thiazide diuretics)
  • if you block, gradient still the same
• Ca channel at apical membrane side
• Na/K pump into blood
• Na/Ca antiport (Na into cell) (Ca into blood)

principal cells

intercalated cells

• Na channel (into cell)
• K channel (out of cell into urine)
• aquaporin on urine side and blood side (if ADH and aldosterone)
• Na/K pump

• K/H antiport (K into cell) (H into urine)
• K channel (into blood)
• HCO3/Cl antiport (Cl into cell) (HCO3 into blood)
• H/ATP pump

PCT

• water reabsorbed 5% during water leading and 24%+ during dehydration
• sodium reabsorbed 4-5%

• hydrostatic pressure in glomerular capillaries leads to increase filtration
• decreases reabsorption (we dont need all that fluid)

• decrease filtration due to decrease hydrostatic pressure of glomerular capillaries
• increased reabsortpion due to increase in oncotic pressure and decrease hydrostatic pressure

• increases in ultrafiltrate lead to lower hydrostatic pressure and greater reabsorption
• asures constant fraction of ultrafiltrate is reabsorbed
  • due to changes in oncotic and hydrostatic pressures in peritubular capillaries with changes in GFR