title: Renal interstitial Ca2+ during sodium loading of normotensive and Dahl-salt hypertensive rats.
abstract: It is now established that cells in many tissues including renal epithelial cells and perivascular sensory nerves have mechanisms that monitor and respond to the concentration of Ca2+ in the interstitial compartment [Ca2+(ISF)]. We tested the hypothesis that high Na+ intake alters renal [Ca2+(ISF)] and that the response is altered in salt-sensitive hypertensive versus normotensive rats. Male Wistar (W), Dahl salt-resistant (DR), and Dahl salt-sensitive (DS) rats were fed diets containing 0.45% or 8% NaCl for 7 days beginning at 8 to 10 weeks of age. Systolic blood pressure (BP) was measured before and at the end of the 7-day period. During the last 12 h the animals were placed in metabolic cages for urine collection. They were then anesthetized and renal [Ca2+(ISF)] was determined using in situ microdialysis. Feeding 8% NaCl caused a significant increase in systolic BP only in DS. The 8% NaCl also caused a significant increase in renal urinary Na+ excretion in all groups, had no effect on renal Ca2+ excretion in W or DS and significantly increased urinary Ca2+ excretion in DR. When fed 0.45% NaCl, renal [Ca2+(ISF)] was lower in W and DR compared with DS. Feeding 8% NaCl significantly increased [Ca(ISF)] in W, had no effect on this parameter in DR, and significantly decreased [Ca2+(ISF)] in DS ([Ca2+(ISF)] for DS on 0.45% NaCl = 1.89 +/- 0.15 v 8% NaCl = 1.08 +/- 0.07 mmol/L, n = 6 to 12, P <.05). These results indicate that Na+ loading significantly alters renal [Ca2+(ISF)]; that the response of DS is disturbed relative to controls, and are consistent with the hypothesis that Na+ loading can alter cell function by modulating [Ca2+(ISF)].
authors.affiliation: Cardiovascular Disease Research Program, Biomedical/Biotechnology Research Institute, North Carolina Central University, 700 George Street, Durham, NC 27707, USA .
authors.forename: Cassandra E
authors.initials: CE
authors.lastname: Palmer
authors.forename: M Audrey
authors.initials: MA
authors.lastname: Rudd
authors.forename: Richard D
authors.initials: RD
authors.lastname: Bukoski
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000652:urine; D001794:Blood Pressure / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D004039:Diet, Sodium-Restricted; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D045604:Extracellular Fluid / Q000187:drug effects* / Q000378:metabolism*; D006973:Hypertension / Q000378:metabolism*; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism*; D008297:Male; D008955:Models, Cardiovascular; D009318:Natriuresis / Q000187:drug effects; D051381:Rats; D020303:Rats, Inbred Dahl; D017208:Rats, Wistar; D012982:Sodium, Dietary / Q000008:administration & dosage*; D013223:Statistics as Topic; D013599:Systole / Q000187:drug effects
chemical_list: D015415:Biomarkers; D012982:Sodium, Dietary; D002118:Calcium