Angiotensin II: a potent regulator of acidification in the rat early proximal convoluted tubule.
The early proximal convoluted tubule (PCT) is the site of 50% of bicarbonate reabsorption in the nephron, but its control by angiotensin II has not been previously studied. In vivo microperfusion was used in both the early and late PCT in Munich-Wistar rats. Systemic angiotensin II administration (20 ng/kg X min) or inhibition of endogenous angiotensin II activity with saralasin (1 microgram/kg X min) caused profound changes in bicarbonate absorption in the early PCT (169 +/- 25 and -187 +/- 15 peq/mm X min, respectively). Because the bicarbonate absorptive capacity of the early PCT under free-flow conditions is 500 peq/mm X min, angiotensin II administration or inhibition affected greater than 60% of proton secretion in this segment. Both agents less markedly affected bicarbonate absorption in the late PCT (+/- 28 peq/mm X min) or chloride absorption (+/- 68-99 peq/mm X min) in both the early and late PCT. Because of its potential for controlling the majority of bicarbonate absorption in the early PCT (hence greater than or equal to 30% of bicarbonate absorption in the entire nephron), angiotensin II may be a powerful physiologic regulator of renal acidification.
D000042:Absorption; D000804:Angiotensin II / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012504:Saralasin / Q000494:pharmacology
D001639:Bicarbonates; D002712:Chlorides; D000804:Angiotensin II; D012504:Saralasin