title: Angiotensin II stimulation of hydrogen ion secretion in the rat early proximal tubule. Modes of action, mechanism, and kinetics.
abstract: Physiologic concentrations of angiotensin II stimulate sodium transport by intestinal and renal early (S1) and late (S2) proximal tubule epithelial cells. We recently found that hydrogen ion secretion, which effects sodium bicarbonate absorption, was a transport function preferentially and potently increased by angiotensin II in S1 cells. S1 cells are normally responsible for half of the total renal hydrogen ion secretion. The mechanism by which angiotensin II regulates intestinal sodium transport is by potentiating sympathetic nerve activity and norepinephrine release. Direct control of hydrogen ion secretion by angiotensin II via receptors on epithelial cells has not been previously demonstrated. We now report that stimulation of in vivo hydrogen ion secretion in the rat early proximal tubule by angiotensin II was not mediated via change in nerve activity. Rather, enhanced hydrogen ion secretion by angiotensin II correlated with increased angiotensin II receptor density on epithelial cells in the early compared to late microdissected proximal tubule. Basolateral as well as luminal angiotensin II stimulated bicarbonate absorption. Angiotensin II reduced bicarbonate permeability and caused alteration in the apparent substrate affinity, but not maximal capacity, of the proximal hydrogen ion secretory system involving the Na+/H+ antiporter.
authors.affiliation: Department of Medicine, University of California, San Francisco 94143.
authors.forename: F Y
authors.initials: FY
authors.lastname: Liu
authors.forename: M G
authors.initials: MG
authors.lastname: Cogan
mesh_terms: D000804:Angiotensin II / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D001639:Bicarbonates / Q000493:pharmacokinetics; D002352:Carrier Proteins / Q000502:physiology; D002463:Cell Membrane Permeability; D006863:Hydrogen-Ion Concentration; D007687:Kidney Tubules, Proximal / Q000294:innervation / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D011522:Protons; D051381:Rats; D011919:Rats, Inbred Strains; D011945:Receptors, Angiotensin / Q000032:analysis; D017923:Sodium-Hydrogen Exchangers; D013564:Sympathetic Nervous System / Q000502:physiology
chemical_list: D001639:Bicarbonates; D002352:Carrier Proteins; D011522:Protons; D011945:Receptors, Angiotensin; D017923:Sodium-Hydrogen Exchangers; D000804:Angiotensin II