title: Development of an AT2-deficient proximal tubule cell line for transport studies.
abstract: Angiotensin II is a major regulatory peptide for proximal tubule Na(+) reabsorption acting through two distinct receptor subtypes: AT(1) and AT(2). Physiological or pathological roles of AT(2) have been difficult to unravel because angiotensin II can affect Na(+) transport either directly via AT(2) on luminal or peritubular plasma membranes of proximal tubule cells or indirectly via the renal vasculature. Furthermore, separate systemic and intratubular renin-angiotensin systems impart considerable complexity to angiotensin's regulation. A transport-competent, proximal tubule cell model that lacks AT(2) is a potentially useful tool to assess cellular angiotensin II regulation. To this end, AT(2)-receptor-deficient mice were bred with an Immortomouse, which harbors the thermolabile immortalization gene SV40 large-T antigen (Tag), and AT(2)-receptor-deficient [AT(2) (-/-)], Tag heterozygous [Tag (+/-)] F(2) offspring were selected for cell line generation. S1 proximal tubule segments were microdissected, and epithelial cell outgrowth was expanded in culture. Cells that formed confluent, electrically resistive monolayers were selected for cryopreservation, and one isolate was extensively characterized for conductance (2 mS/cm(2)), short-circuit current (Isc; 0.2 microA/cm(2)), and proximal tubule-specific Na3(+) - succinate (DeltaIsc = 0.8 microA/cm(2) at 2 mM succinate) and Na3(+) - phosphate cotransport (DeltaIsc = 3 microA/cm(2) at 1 mM phosphate). Light microscopy showed a uniform, cobblestone-shaped monolayer with prominent cilia and brush borders. AT(2) receptor functionality, as demonstrated by angiotensin II inhibition of ANF-stimulated cGMP synthesis, was absent in AT(2)-deficient cells but prominent in wild-type cells. This transport competent cell line in conjunction with corresponding wild type and AT(1)-deficient lines should help explain angiotensin II signaling relevant to Na(+) transport.
authors.affiliation: Department of Physiology and Biophysics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-4970, USA. woostp@ccf.org
authors.forename: Philip G
authors.initials: PG
authors.lastname: Woost
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Kolb
authors.forename: Chung-Ho
authors.initials: CH
authors.lastname: Chang
authors.forename: Margaret
authors.initials: M
authors.lastname: Finesilver
authors.forename: Tadashi
authors.initials: T
authors.lastname: Inagami
authors.forename: Ulrich
authors.initials: U
authors.lastname: Hopfer
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D015139:Blotting, Southern; D001947:Breeding; D002460:Cell Line; D004573:Electrolytes; D004594:Electrophysiology; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D005260:Female; D005838:Genotype; D006162:Guanylate Cyclase / Q000378:metabolism; D015151:Immunoblotting; D007150:Immunohistochemistry; D007687:Kidney Tubules, Proximal / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D051379:Mice; D044139:Receptor, Angiotensin, Type 2 / Q000172:deficiency*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014909:Wheat Germ Agglutinins / Q000378:metabolism
chemical_list: D004573:Electrolytes; D044139:Receptor, Angiotensin, Type 2; D014909:Wheat Germ Agglutinins; D000804:Angiotensin II; D006162:Guanylate Cyclase