Hormonal regulation of renal sodium and water excretion during normotensive sodium loading in conscious dogs.
Saline was infused intravenously for 90 min to normal, sodium-replete conscious dogs at three different rates (6, 20, and 30 micromol x kg(-1) x min(-1)) as hypertonic solutions (HyperLoad-6, HyperLoad-20, and HyperLoad-30, respectively) or as isotonic solutions (IsoLoad-6, IsoLoad-20, and IsoLoad-30, respectively). Mean arterial blood pressure did not change with any infusion of 6 or 20 micromol x kg(-1) x min(-1). During HyperLoad-6, plasma vasopressin increased by 30%, although the increase in plasma osmolality (1.0 mosmol/kg) was insignificant. During HyperLoad-20, plasma ANG II decreased from 14+/-2 to 7+/-2 pg/ml and sodium excretion increased markedly (2.3+/-0.8 to 19+/-8 micromol/min), whereas glomerular filtration rate (GFR) remained constant. IsoLoad-20 decreased plasma ANG II similarly (13+/-3 to 7+/-1 pg/ml) concomitant with an increase in GFR and a smaller increase in sodium excretion (1.9+/-1.0 to 11+/-6 micromol/min). HyperLoad-30 and IsoLoad-30 increased mean arterial blood pressure by 6-7 mm Hg and decreased plasma ANG II to approximately 6 pg/ml, whereas sodium excretion increased to approximately 60 micromol/min. The data demonstrate that, during slow sodium loading, the rate of excretion of sodium may increase 10-fold without changes in mean arterial blood pressure and GFR and suggest that the increase may be mediated by a decrease in plasma ANG II. Furthermore, the vasopressin system may respond to changes in plasma osmolality undetectable by conventional osmometry.
Sandgaard
N C
NC
Department of Medical Physiology, University of Copenhagen, DK-2200 Copenhagen, Denmark.
Andersen
J L
JL
Bie
P
P
D000804:Angiotensin II / Q000097:blood / Q000502:physiology*; D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D001798:Blood Proteins / Q000032:analysis; D003404:Creatinine / Q000097:blood; D004231:Diuresis / Q000187:drug effects* / Q000502:physiology; D004285:Dogs; D004573:Electrolytes / Q000097:blood; D005260:Female; D005919:Glomerular Filtration Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects; D007552:Isotonic Solutions / Q000008:administration & dosage / Q000494:pharmacology; D007668:Kidney / Q000187:drug effects / Q000502:physiology; D009318:Natriuresis / Q000187:drug effects* / Q000502:physiology; D009994:Osmolar Concentration; D012016:Reference Values; D012462:Saline Solution, Hypertonic / Q000008:administration & dosage / Q000494:pharmacology; D012964:Sodium / Q000008:administration & dosage / Q000494:pharmacology*; D014667:Vasopressins / Q000097:blood / Q000502:physiology*
D001798:Blood Proteins; D004573:Electrolytes; D007552:Isotonic Solutions; D012462:Saline Solution, Hypertonic; D014667:Vasopressins; D000804:Angiotensin II; D012964:Sodium; D003404:Creatinine