title: Gastrointestinal osmoreceptors and renal sodium excretion in humans.
abstract: The hypothesis that natriuresis can be induced by stimulation of gastrointestinal osmoreceptors was tested in eight supine subjects on constant sodium intake (150 mmol NaCl/day). A sodium load equivalent to the amount contained in 10% of measured extracellular volume was administered by a nasogastric tube as isotonic or hypertonic saline (850 mM). In additional experiments, salt loading was replaced by oral water loading (3.5% of total body water). Plasma sodium concentration increased after hypertonic saline (+3.1 +/- 0.7 mM), decreased after water loading (-3.8 +/- 0.8 mM), and remained unchanged after isotonic saline. Oncotic pressure decreased by 9.4 +/- 1.2, 3.7 +/- 1.2, and 10.7 +/- 1.3%, respectively. Isotonic saline induced an increase in renal sodium excretion (104 +/- 15 to 406 +/- 39 micromol/min) that was larger than seen with hypertonic saline (85 +/- 15 to 325 +/- 39 micromol/min) and water loading (88 +/- 11 to 304 +/- 28 micromol/min). Plasma ANG II decreased to 22 +/- 6, 35 +/- 6, and 47 +/- 5% of baseline after isotonic saline, hypertonic saline, and water loading, respectively. Plasma atrial natriuretic peptide (ANP) concentrations and urinary excretion rates of endothelin-1 were unchanged. In conclusion, stimulation of osmoreceptors by intragastric infusion of hypertonic saline is not an important natriuretic stimulus in sodium-replete subjects. The natriuresis after intragastric salt loading was independent of ANP but can be explained by inhibition of the renin-angiotensin system.
authors.affiliation: Department of Medical Physiology, Panum Institute, University of Copenhagen, DK-2200 Copenhagen, Denmark.
authors.forename: L J
authors.initials: LJ
authors.lastname: Andersen
authors.forename: T U
authors.initials: TU
authors.lastname: Jensen
authors.forename: M H
authors.initials: MH
authors.lastname: Bestle
authors.forename: P
authors.initials: P
authors.lastname: Bie
mesh_terms: D000328:Adult; D000804:Angiotensin II / Q000097:blood; D009320:Atrial Natriuretic Factor / Q000097:blood; D004068:Digestive System Physiological Phenomena; D004326:Drinking / Q000502:physiology; D019332:Endothelin-1 / Q000652:urine; D006801:Humans; D007441:Intubation, Gastrointestinal; D007552:Isotonic Solutions / Q000008:administration & dosage / Q000494:pharmacology; D007668:Kidney / Q000378:metabolism*; D008297:Male; D012462:Saline Solution, Hypertonic / Q000008:administration & dosage / Q000494:pharmacology; D012964:Sodium / Q000652:urine*; D012965:Sodium Chloride / Q000008:administration & dosage / Q000494:pharmacology; D014882:Water-Electrolyte Balance / Q000502:physiology*
chemical_list: D019332:Endothelin-1; D007552:Isotonic Solutions; D012462:Saline Solution, Hypertonic; D000804:Angiotensin II; D012965:Sodium Chloride; D009320:Atrial Natriuretic Factor; D012964:Sodium