title: Effect of luminal angiotensin II on rabbit proximal convoluted tubule bicarbonate absorption.
abstract: The present in vitro microperfusion study examined the effect of luminal angiotensin II on proximal convoluted tubule (PCT) volume absorption and bicarbonate transport. Neither 10(-11) M, 10(-10) M, nor 2 x 10(-8) M luminal angiotensin II significantly affected PCT transport. When tubules were first perfused with enalaprilat to inhibit endogenous angiotensin II production, addition of 10(-10) M luminal angiotensin II increased volume absorption (0.72 +/- 0.08 vs. 0.86 +/- 0.07 nl x mm(-1) xmin(-1), P < 0.01) and bicarbonate transport (52.3 +/- 3.7 vs. 67.9 +/- 4.2 pmol x mm(-1) min(-1), P < 0.01). Addition of 10(-6) M losartan, an AT1 inhibitor, to the luminal perfusate inhibited volume absorption (0.95 +/- 0.14 vs. 0.72 +/- 0.11 nl x mm(-1) x min(-1), P < 0.05) and bicarbonate transport (65.0 +/- 7.3 vs. 54.7 +/- 9.2 pmol x mm(-1) x min(-1), P < 0.05). Addition of 10(-4) M luminal PD-123319, an AT2 inhibitor, was without effect. In tubules perfused with 10(-4) M luminal enalaprilat and 10(-4) M luminal PD-123319, addition of 10(-10) M luminal angiotensin II in the experimental period resulted in a stimulation in volume absorption (0.61 +/- 0.08 vs. 0.81 +/- 0.10 nl x mm(-1) x min(-1), P < 0.01) and bicarbonate transport (49.9 +/- 6.3 vs. 77.4 +/- 14.3 pmol x mm(-1) x min(-1), P < 0.01). In tubules perfused with 10(-6) M losartan and 10(-4) M enalaprilat, addition of luminal 10(-10) M angiotensin II resulted in no change in transport. These data are consistent with endogenous angiotensin II affecting PCT bicarbonate transport in vitro via luminal AT1 receptors.
authors.affiliation: Department of Pediatrics, University of Texas Southwestern Medical Center at Dallas, 75235-9063, USA.
authors.forename: M
authors.initials: M
authors.lastname: Baum
authors.forename: R
authors.initials: R
authors.lastname: Quigley
authors.forename: A
authors.initials: A
authors.lastname: Quan
mesh_terms: D000042:Absorption / Q000187:drug effects; D000804:Angiotensin II / Q000494:pharmacology*; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D015773:Enalaprilat / Q000494:pharmacology; D005260:Female; D007093:Imidazoles / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D019808:Losartan / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D011817:Rabbits
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D001639:Bicarbonates; D007093:Imidazoles; D011725:Pyridines; D000804:Angiotensin II; C073402:PD 123319; D015773:Enalaprilat; D019808:Losartan