title: Renal function at steady state in a toad (Bufo viridis) acclimated in hyperosmotic NaCl and urea solutions.
abstract: Kidney function of the euryhaline toad Bufo viridis was studied in animals acclimated to tap water and solutions of NaCl (230 and 500 mosmol.kg-1 H2O) and urea (500 mmol.l-1) in steady-state conditions. An ureter was catheterized for continuous urine collection and blood was sampled from an iliac artery. A single injection of 3H-inulin served for estimation of glomerular filtration rate: this was in the range of 15-27 ml.kg-1.h-1 and did not differ significantly in any of the acclimation conditions. Urine flow, on the other hand, varied considerably and was highest in tap water (18.2 +/- 3.2 ml.kg-1.h-1; urine/plasma inulin ratio = 0.88), lower in 230 mosmol.kg-1 H2O NaCl solution (13.5 +/- 3.9 ml.kg-1.h-1; u/p inulin ratio = 1.73) and lowest in 500 mosmol.kg-1 H2O NaCl or urea acclimation solutions (5-7 ml.kg-1.h-1; u/p inulin = 3.7-4.2). Clearance of free water was high in the tap water group, lower in 230 mosmol.kg-1 H2O NaCl solution, and much lower in the hyperosmotic acclimation conditions. Clearances of both Na+ and Cl- were similar under our experimental conditions, but changed independently in accordance to the composition of the acclimation solution. Potassium clearance was similar in all acclimation conditions, and a constant plasma K+ concentration was maintained. Urea clearance was high in tap water and 500 mmol.l-1 urea acclimation groups and low in the NaCl acclimations.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Biology, Technion-Israel Institute of Technology, Haifa.
authors.forename: S
authors.initials: S
authors.lastname: Shpun
authors.forename: U
authors.initials: U
authors.lastname: Katz
mesh_terms: D000818:Animals; D002025:Bufonidae / Q000502:physiology*; D005260:Female; D005919:Glomerular Filtration Rate; D007668:Kidney / Q000502:physiology*; D008297:Male; D012462:Saline Solution, Hypertonic; D014508:Urea / Q000097:blood / Q000652:urine; D014867:Water; D014882:Water-Electrolyte Balance / Q000502:physiology*
chemical_list: D012462:Saline Solution, Hypertonic; D014867:Water; D014508:Urea