True about the H+ secretion by the PCT is:

(C) It is meant for reabsorption of filtered bicarbonate (A) Acidification of urine is done by collecting ducts. H+ secretion in PCT occurs along the concentration gradient. In collecting ducts H+ secretion is against concentration gradient Diffusion trapping occurs in collecting ducts not in PCT. H+ secretion in PCT is meant for reabsorption of bicarbonate. Amount of filtered is calculated by (per unit time) Px x GFRPx = plasma concentration of substance. How much bicarbonate is filtered per unit time is 24meq/lit X 180L/day =4320meq/day Most of this is reabsorbed in PCT HCO3- is ionic. Ionic substances are less diffusible. So, first it is conveed to non-ionic form. For this H+ is secreted by PCT. H+ is secreted in equal amounts of HCO3- (i.e 4320 meq/day) In addition, PCT secretes 80meq/day of H+(: 4320 + 80 =4400meq/day) .This is net acid output.