Glomerular filtration rate (GFR) is favoured (directly proportional) by:
Ans. a (Intracapillary glomerular pressure ). (Ref. Guyton 11th /320; 322; Table 26-4; Ganong 22nd /707)GLOMERULAR FILTRATION RATE (GFR)# Inulin is freely filtered and is neither reabsorbed nor secreted.GFR = UV/PWhere, U--concentration in urineV--volume of urine passed/minuteP--concentration in plasma.# Clinically, creatinine clearance is good measure of GFR.FACTORS THAT CAN DECREASE THE GLOMERULAR FILTRATION RATE (GFR) include:Physical DeterminantsPhysiologic/Pathophysiologic Causes| Kf (glomerular filtration coefficient) -|GFRRenal disease, DM, Hypertension| PB (Bowman's capsule hydrostatic pressure) -| GFRUrinary tract obstruction (e.g., kidney stones)| paiG (glomerular capillary colloid osmotic pressure) -| GFR | Renal blood flow, | plasma proteins|PG (glomerular capillary hydrostatic pressure) -|GFR|AP -|PG|Arterial pressure (has only small effect due to autoregulation)| RE -| PG| Angiotensin II (drugs that block angiotensin II formation)| RA-|PGT Sympathetic activity, vasoconstrictor hormones (e.g., norepinephrine, endothelin)FACTORS THAT AFFECT GFR fGFR: Kf x (Pgc - Pco - Pt)l1. Intracapillary glomerular pressure (Pgc):It is determined by the systemic arterial pressure and the tone of the pre- glomerular and post-glomerular arterioles. It is the most important GFR modulator.2. Intracapillary oncotic pressure (Pco):It is low in malnutrition and following plasma volume expansion with Ringer's solutions. It is high in dehydrated states and primary hyperproteinemia.3. Intra-capsular glomerular pressure (Pt):It is normally close to zero, however, it increases in urinary obstruction i.e tubular protein casts, urinary stones, tumors, prostatic hypertrophy, congenital abnormalities of the lower urinary tract, etc.4. Filtration coefficient (Kf):It is a function of the total number and the size of "pores" in the glomerular sieve. It is lowered by vasoactive substances that cause the glomerular filtration area to decrease. Angiotensin II, for example induce contraction of mesangial cells causing decreased glomerular capillary area. The Kf of superficial glomeruli is higher than that of deep glomeruli.Hormones and Autacoids That Influence Glomerular Filtration Rate (GFR):Hormone or AutacoidEffect on GFRNorepinephrine|Epinephrine|Endothelin4Angiotensin II(prevents |)Endothelial-derived nitric oxide|Prostaglandins|Also remember:Glomerular filtration rate GFR = Uinulin XV----P inulln= CinulinGlomerular filtration rate GFR = Kf Effective renal plasma flow ERPF= UPAH XV---PPAH= CPAHRenal blood flow RBF=RPF----1-Hct Filtration fraction FF =GFR----RPF Free water clearance CH2O=V-Cosm.
Intracapillary glomerular pressure
Oncotic pressure
Bowman's capsular hydrostatic pressure
All of the above
Kidneys and Body Fluids