GFR = Kf (net filtration pressure) = Kf (Pgc - Pbc - *gc ) Pgc *gc af ~~~~~~~~~~~~~~~ef Pbc
Kf - water permeability - total surface area for filtration GFR= 120 ml/min ? liters/day Mesangial cells ECF , (TBW, 42 liters)
When renal sympathetic nerve is stimulated, the glomerular capillary hydrostatic pressure A. will increase B. will decrease C. may or may not decrease D. I don’t like Starling
D. this question stimulates my para-sympathetic and makes
me want to pee
Net Filtration Pressure
gender body size age
ml/min per 1.73m2
30 - 300mg per day
Proteinuria; > 300 mg/day
How much of urine do you Secrete and Excrete in a day?
GFR 180 liters/day
GFR, Clearance, Renal Autoreg,
Renal Handling of Glucose
Freely filtered : solute filtered with the plasma water Px = BCx Filtered ‘Load’ : rate of filtration of a solute GFR multiply Px (mg/time) Excreted Load : rate of excretion : Urine flow rate, V multiply Ux
Excreted load/plasma [ ]
- What is excreted is cleared from the plasma into the urine -What is excreted must have originally come from the plasma -What ‘volume of plasma’ has been cleared of this amount of excreted solute found in urine - ‘Renal clearance’
Filtered load = Excreted load GFR x PIN = V x UIN
GFR = =
UIN x V / PIN
the excreted load ‘cleared’ of a volume of plasma/time
GFR = Renal Clearance of Inulin
James Augustine Shannon 1904-1994
Inulin, a biologically inert polysaccharide, can be used to estimate the glomerular filtration rate since it is filtered, but not reabsorbed or secreted.
Renal Clearance…… is it Clear?
Clearance of plasma protein z _ E=z_ Clearance of glucose F = z_ z_ E= z_ _ /_ F = GFR x PG _ /_
Clearance = Excr load, UxV/ [Plasma]x = ml [plasma] / min
CCr = Ucr .V/ PCr
Plasma creatinine level vs. GFR
GFR . Px = Filtered ‘load’
Changes in GFR …
Renal Autoregulation GFR RBF
JG ( AfArt ) ( McD )
The intersection of the macula densa in the distal tubule with the afferent arteriole forms the juxtaglomerular apparatus, which secretes the endocrine signal known as renin into blood at the afferent arteriole.
- Myogenic - McD (t-g fdbk)
Renal Autoregulation Maintains RBF GFR (60-150 mmHg)
changes in same direction [*gc ]
F = P mmHg / R
Intrinsic property; minus nerve / hormone actions
Renal sympathetic nerve activity overrides (masked) renal autoregulation
2) Tubulo-glomerular feedback
McD Juxta GA adenosine
myogenic (distal) t - g fdbk
Autoregulation (McD release paracrine vasoC to afArt)
JGApp Volume Regulation Sodium Balance (McD release a renin modulator to JG cells of AfArt)
Substance X is filtered and secreted but not reabsorbed. Substance Y is filtered and some of it is reabsorbed. Substance Z is filtered and completely reabsorbed.
The luminal section of the plasma membrane of the tubule cells faces the filtrate, whereas the basolateral section is in close proximity to the peritubular capillary.
Reabsorb about 65 percent of the filtered sodium, chloride, bicarbonate, and potassium and essentially al the filtered glucose and amino acids. Secrete organic acids, bases, and hydrogen ions into the tubular lumen.
2o active transport
Renal handling of Glucose Filtered Glucose Load : GFR x Pglu Reabsorbed Glucose = Filtered Glucose No glucosuria (excreted Uglu.V = 0 mg/min)
Max Reabsorbed Glucose = GFR x #Pglu TmGlu = GFR x #Pglu
# renal plasma threshold for glucose
When filtered glucose load (GFR. Pglu) exceeds the...