Long-Term Regulation of Vacuolar H+-ATPase by Angiotensin II in Proximal Tubule Cells

The function of the kidney is to keep constant the volume and

composition of the body fluids, by filtering the entire plasma volume

every 30 minutes and reabsorbing approximately two-thirds of the

filtrate in the proximal tubule (PT) [1, 2]. The glomerular filtrate

enters the lumen of the PT, and the majority of filtered sodium

and HCO−3 are reclaimed along the early (S1) and convoluted (S2) portions of the PT in a manner coupled to the secretion of H+ into the lumen [2]. Furthermore, large amounts of chloride and water

are also reabsorbed in this nephron segment. Considering the role

of PTs and other nephron segments, less than 1% of water, sodium,

chloride, and variable amounts of other solutes are excreted in the

urine.