title: Characteristics of ionic binding by rat renal tissue in vitro.
abstract: A study has been made of Na+ and Cl- binding in metabolically inhibited slices of rat renal cortex and outer medulla incubated in modified Krebs phosphate-bicarbonate Ringer solution. At pH 7.35 in control media (cortex, 147 mmol Na+/l, 105 mmol Cl-/l; outer medulla, 187 mmol Na+/l, 145 mmol Cl-/l) cortical slices bound (mean) 171 nmol Na+ and 56.7 nmol Cl-/mg solute-free dry weight; outer medullary slices bound 188 nmol Na+/mg and negligible amounts of Cl-. In both regions, Na+ was exchangeable on a 1:1 basis for K+ or Li+ in media containing equal concentrations of each cation: Na+ was completely displaced by La3+. In cortical slices in media containing equimolar Cl- and other monovalent anions, binding occurred according to the sequence acetate less than or equal to salicylate less than or equal to Cl- less than SCN-; Cl- was completely displaced by PO4(3-). When medium pH was lowered, Na+ binding was markedly reduced in both regions, whereas Cl- binding increased (and became significant in outer medulla). In NaCl solutions, Na+ binding capacity was saturated at control Na+ concentrations. When [Na+] was progressively reduced (iso-osmolality being maintained by addition of urea), bound Na+ in both regions was nearly linearly related to log medium [Na+]. Raising medium osmolality with urea caused decreased Na+ binding and increased Cl- binding in both regions. Na+ binding in both regions was significantly reduced by pre-treatment with chondroitinase ABC. Binding of both ions was independent of temperature within the range 2-37 degrees C. The possibility is raised that renal ionic binding might influence vectorial ion transport by affecting free ion activity in the region of the transporting cells.
mesh_terms: D000818:Animals; D000838:Anions / Q000494:pharmacology; D001667:Binding, Competitive / Q000187:drug effects; D002712:Chlorides / Q000378:metabolism*; D003080:Cold Temperature; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007668:Kidney / Q000378:metabolism*; D007672:Kidney Cortex / Q000378:metabolism; D007679:Kidney Medulla / Q000378:metabolism; D008297:Male; D009994:Osmolar Concentration; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism*
chemical_list: D000838:Anions; D002712:Chlorides; D012964:Sodium