Increased filtration fraction-increasing filtration fraction means that a larger portion of the renal plasma flow (rpf) is filtered across the glomerular capillaries. this increased flow causes an increase in the protein concentration and oncotic pressure of the blood leaving the glomerular capillaries. this blood becomes the peritubular capillary blood supply. the increased oncotic pressure in the peritubular capillary blood is a driving force favoring reabsorption in the proximal tubule. extracellular fluid (ecf) volume expansion, decreased peritubular capillary protein concentration, and increased peritubular capillary hydrostatic pressure all inhibit proximal reabsorption. oxygen deprivation would also inhibit reabsorption by stopping the na+-k+ pump in the basolateral membranes.
