title: ET(B) receptor in renal medulla is enhanced by local sodium during low salt intake.
abstract: Renal endothelin-1 participates in sodium and water handling, and its urinary excretion is increased in sodium-retentive states. We compared the cortical and medullary renal expression of prepro-endothelin-1, endothelin-converting enzyme-1, and endothelin type A and type B receptors in patients who underwent nephrectomy after normal (108 mmol/d NaCl; n=6) or low (20 mmol/d NaCl; n=6) sodium diet and investigated whether sodium exerts a direct role on endothelin receptor binding in vitro. With normal sodium diet prepro-endothelin-1 mRNA was 3-fold higher in renal medulla than in cortex (P<0.01), whereas endothelin-converting enzyme-1 mRNA was equally distributed. Endothelin-1 receptor density was 2-fold higher in renal medulla than in cortex (P<0.05). Type B was the main receptor subtype in both regions. In the renal cortex, low sodium diet caused a 194% increase in prepro-endothelin-1 mRNA (P<0.05), whereas endothelin-converting enzyme-1 type B and type A receptors remained unchanged. In contrast, in the renal medulla the increase in prepro-endothelin-1 mRNA (+30%, P<0.05) was associated with a selective increase in type B receptor for both mRNA expression (+37%, P<0.05) and binding density (+55%, P<0.05). Increasing in vitro sodium concentrations between 154 and 308 mmol/L significantly enhanced type B receptor density (P<0.05) and affinity (P<0.05). In conclusion, during low sodium diet, renal prepro-endothelin-1 synthesis increases mainly in the renal cortex (where no changes in receptors occur), whereas type B receptor is selectively enhanced in the renal medulla. The range of sodium concentrations that are physiologically present in vivo in the renal medulla selectively modulate type B receptor density and affinity.
authors.affiliation: Clinica Medica e Cardiologia, University of Florence, Italy.
authors.forename: Simone
authors.initials: S
authors.lastname: Vanni
authors.forename: Gianluca
authors.initials: G
authors.lastname: Polidori
authors.forename: Ilaria
authors.initials: I
authors.lastname: Cecioni
authors.forename: Sergio
authors.initials: S
authors.lastname: Serni
authors.forename: Marco
authors.initials: M
authors.lastname: Carini
authors.forename: Pietro Amedeo
authors.initials: PA
authors.lastname: Modesti
mesh_terms: D016282:Aspartic Acid Endopeptidases / Q000235:genetics; D001667:Binding, Competitive; D019332:Endothelin-1 / Q000378:metabolism; D000072396:Endothelin-Converting Enzymes; D016232:Endothelins / Q000235:genetics; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D007672:Kidney Cortex / Q000187:drug effects / Q000378:metabolism; D007679:Kidney Medulla / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008666:Metalloendopeptidases; D008875:Middle Aged; D011498:Protein Precursors / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011869:Radioligand Assay; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012964:Sodium / Q000378:metabolism*; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage*
chemical_list: D019332:Endothelin-1; D016232:Endothelins; D007457:Iodine Radioisotopes; D011498:Protein Precursors; D012333:RNA, Messenger; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin; D017673:Sodium Chloride, Dietary; D012964:Sodium; D016282:Aspartic Acid Endopeptidases; D008666:Metalloendopeptidases; C000606923:ECE1 protein, human; D000072396:Endothelin-Converting Enzymes