<prompt> Glomerular filtration rate GFR is favoured directly proportional by:Intracapillary glomerular pressureOncotic pressureBowmans capsular hydrostatic pressureAll of the above  <response>: Ans. a Intracapillary glomerular pressure . Ref. Guyton 11th 320; 322; Table 26-4; Ganong 22nd 707GLOMERULAR FILTRATION RATE GFR Inulin is freely filtered and is neither reabsorbed nor secreted.GFR UVPWhere, U--concentration in urineV--volume of urine passedminuteP--concentration in plasma. Clinically, creatinine clearance is good measure of GFR.FACTORS THAT CAN DECREASE THE GLOMERULAR FILTRATION RATE GFR include:Physical DeterminantsPhysiologicPathophysiologic Causes Kf glomerular filtration coefficient -GFRRenal disease, DM, Hypertension PB Bowmans capsule hydrostatic pressure - GFRUrinary tract obstruction e.g., kidney stones paiG glomerular capillary colloid osmotic pressure - GFR Renal blood flow, plasma proteinsPG glomerular capillary hydrostatic pressure -GFRAP -PGArterial 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, endothelinFACTORS THAT AFFECT GFR fGFR: Kf x Pgc - Pco - Ptl1. 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 Ringers 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 GFRNorepinephrineEpinephrineEndothelin4Angiotensin IIprevents Endothelial-derived nitric oxideProstaglandinsAlso 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 RBFRPF---1-Hct Filtration fraction FF GFR---RPF Free water clearance CH2OV-Cosm. 