title: Prolonged hypobaric hypoxemia attenuates vasopressin secretion and renal response to osmostimulation in men.
abstract: Effects of hypobaric hypoxemia on endocrine and renal parameters of body fluid homeostasis were investigated in eight normal men during a sojourn of 8 days at an altitude of 4,559 m. Endocrine and renal responses to an osmotic stimulus (5% hypertonic saline, 3.6 ml/kg over 1 h) were investigated at sea level and on day 6 at altitude. Several days of hypobaric hypoxemia reduced body weight (-2.1 +/- 0.4 kg), increased plasma osmolality (+5.3 +/- 1.4 mosmol/kgH(2)O), elevated blood pressure (+12 +/- 1 mmHg), reduced creatinine clearance (122 +/- 6 to 96 +/- 10 ml/min), inhibited the renin system (19.5 +/- 2.0 to 10.9 +/- 0.9 mU/l) and plasma vasopressin (1.14 +/- 0.16 to 0.38 +/- 0.06 pg/ml), and doubled circulating levels of norepinephrine (103 +/- 16 to 191 +/- 35 pg/ml) and endothelin-1 (3.0 +/- 0.2 to 6.3 +/- 0.6 pg/ml), whereas urodilatin excretion rate decreased from day 2 (all changes P < 0.05 compared with sea level). Plasma arginine vasopressin response and the antidiuretic response to hypertonic saline loading were unchanged, but the natriuretic response was attenuated. In conclusion, chronic hypobaric hypoxemia 1) elevates the set point of plasma osmolality-to-plasma vasopressin relationship, possibly because of concurrent hypertension, thereby causing hypovolemia and hyperosmolality, and 2) blunts the natriuretic response to hypertonic volume expansion, possibly because of elevated circulating levels of norepinephrine and endothelin, reduced urodilatin synthesis, or attenuated inhibition of the renin system.
authors.affiliation: Department of Clinical Physiology, Herlev Hospital, University of Copenhagen, Denmark. mbestle@dadlnet.dk
authors.forename: Morten H
authors.initials: MH
authors.lastname: Bestle
authors.forename: Niels V
authors.initials: NV
authors.lastname: Olsen
authors.forename: Troels D
authors.initials: TD
authors.lastname: Poulsen
authors.forename: Robert
authors.initials: R
authors.lastname: Roach
authors.forename: Niels
authors.initials: N
authors.lastname: Fogh-Andersen
authors.forename: Peter
authors.initials: P
authors.lastname: Bie
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D000450:Aldosterone / Q000097:blood; D000531:Altitude; D001127:Arginine Vasopressin / Q000097:blood / Q000378:metabolism*; D009320:Atrial Natriuretic Factor / Q000097:blood / Q000652:urine; D001794:Blood Pressure; D001835:Body Weight; D003404:Creatinine / Q000097:blood / Q000652:urine; D019332:Endothelin-1 / Q000097:blood; D004837:Epinephrine / Q000097:blood; D006339:Heart Rate; D006801:Humans; D006982:Hypertonic Solutions / Q000008:administration & dosage; D000860:Hypoxia / Q000097:blood / Q000503:physiopathology*; D007262:Infusions, Intravenous; D007668:Kidney / Q000187:drug effects / Q000503:physiopathology*; D007677:Kidney Function Tests; D008297:Male; D009638:Norepinephrine / Q000097:blood; D009994:Osmolar Concentration; D010446:Peptide Fragments / Q000652:urine; D012083:Renin / Q000097:blood; D012965:Sodium Chloride / Q000008:administration & dosage
chemical_list: D019332:Endothelin-1; D006982:Hypertonic Solutions; D010446:Peptide Fragments; D001127:Arginine Vasopressin; D012965:Sodium Chloride; D000450:Aldosterone; C056452:Ularitide; D009320:Atrial Natriuretic Factor; D003404:Creatinine; D012083:Renin; D009638:Norepinephrine; D004837:Epinephrine