Glomular filtration rate increases if: September 2005

Ans. C: Increased renal blood flow GFR = Kf x Net filtration pressure Net filtration pressure represents the sum of the hydrostatic and colloid osmotic forces that either our/oppose filtration across glomerular capillaries Hydrostatic pressure inside the glomerular capillaries (PGC) - Promotes filtration Hydrostatic pressure in the bowman's capsule outside the capillaries (PB)-opposes filtration Colloid osmotic pressure of glomerular capillary plasma proteins-Opposes filtration Colloid osmotic pressure of Bowman's capsule proteins-promotes filtration - Afferent aeriolar constriction will reduce renal blood flow and reduce PGC, causing a reduction in GFR. - Efferent aeriolar constriction will reduce renal blood flow but increase PGC; these changes act in opposite directions with respect to GFR and the net effect on GFR is minimal. - A reduction in Kf will reduce GFR (contraction of mesangial cells and reducing the area available for filtration) - Any given vasoactive agent may have a spectrum of effects (on afferent/efferent aeriolar tone or Kf), making the net effect on GFR difficult to predict. Thus, angiotensin II, a major regulator of glomerular function, causes constriction of both afferent and efferent aerioles, as well as reducing Kf. The overall outcome for GFR depends on the relative magnitudes of these actions, which vary in different pathophysiological conditions. A high protein intake increase renal blood flow and GFR - Large increase in blood glucose levels in uncontrolled D increase renal blood flow and GFR. Kf: Glomerular ultrafiltration coefficient, PGC: mean hydrostatic pressure in glomerular capillaries