title: Long-term space flight simulation reveals infradian rhythmicity in human Na(+) balance.
abstract: The steady-state concept of Na(+) homeostasis, based on short-term investigations of responses to high salt intake, maintains that dietary Na(+) is rapidly eliminated into urine, thereby achieving constant total-body Na(+) and water content. We introduced the reverse experimental approach by fixing salt intake of men participating in space flight simulations at 12 g, 9 g, and 6 g/day for months and tested for the predicted constancy in urinary excretion and total-body Na(+) content. At constant salt intake, daily Na(+) excretion exhibited aldosterone-dependent, weekly (circaseptan) rhythms, resulting in periodic Na(+) storage. Changes in total-body Na(+) (±200-400 mmol) exhibited longer infradian rhythm periods (about monthly and longer period lengths) without parallel changes in body weight and extracellular water and were directly related to urinary aldosterone excretion and inversely to urinary cortisol, suggesting rhythmic hormonal control. Our findings define rhythmic Na(+) excretory and retention patterns independent of blood pressure or body water, which occur independent of salt intake.
authors: Interdisciplinary Center for Clinical Research, Friedrich-Alexander-University, Erlangen-Nürnberg, Glückstrasse 6, D-91054 Erlangen, Germany.
authors: Natalia
authors: N
authors: Rakova
authors: Kathrin
authors: K
authors: Jüttner
authors: Anke
authors: A
authors: Dahlmann
authors: Agnes
authors: A
authors: Schröder
authors: Peter
authors: P
authors: Linz
authors: Christoph
authors: C
authors: Kopp
authors: Manfred
authors: M
authors: Rauh
authors: Ulrike
authors: U
authors: Goller
authors: Luis
authors: L
authors: Beck
authors: Alexander
authors: A
authors: Agureev
authors: Galina
authors: G
authors: Vassilieva
authors: Liubov
authors: L
authors: Lenkova
authors: Bernd
authors: B
authors: Johannes
authors: Peter
authors: P
authors: Wabel
authors: Ulrich
authors: U
authors: Moissl
authors: Jörg
authors: J
authors: Vienken
authors: Rupert
authors: R
authors: Gerzer
authors: Kai-Uwe
authors: KU
authors: Eckardt
authors: Dominik N
authors: DN
authors: Müller
authors: Karl
authors: K
authors: Kirsch
authors: Boris
authors: B
authors: Morukov
authors: Friedrich C
authors: FC
authors: Luft
authors: Jens
authors: J
authors: Titze
mesh_terms: D000328:Adult; D000450:Aldosterone / Q000652:urine; D001794:Blood Pressure; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism; D007477:Ions / Q000737:chemistry; D008297:Male; D010507:Periodicity; D012964:Sodium / Q000652:urine*; D017673:Sodium Chloride, Dietary; D018561:Space Simulation
chemical_list: D007477:Ions; D017673:Sodium Chloride, Dietary; D000450:Aldosterone; D012964:Sodium; D006854:Hydrocortisone