Low urinary albumin excretion in astronauts during space missions.
BACKGROUND
Physiological changes occur in man during space missions also at the renal level. Proteinuria was hypothesized for space missions but research data are missing.


METHODS
Urinary albumin, as an index of proteinuria, and other variables were analyzed in 4 astronauts during space missions onboard the MIR station and on the ground (control). Mission duration before first urine collection in the four astronauts was 4, 26, 26, and 106 days, respectively. On the ground, data were collected 2 months before mission in two astronauts, 6 months after in the other astronauts. A total of twenty-two 24-hour urine collections were obtained in space (n per astronaut = 1-14) and on the ground (n per astronaut = 2-12). Urinary albumin was measured by radioimmunoassay. For each astronaut, mean of data in space and on the ground was defined as individual average.


RESULTS
The individual averages of 24 h urinary albumin were lower in space than on the ground in all astronauts; the difference was significant (mean +/- SD, space and on the ground = 3.41 +/- 0.56 and 4.70 +/- 1.20 mg/24 h, p = 0.017). Dietary protein intake and 24-hour urinary urea were not significantly different between space and on the ground.


CONCLUSIONS
Urinary albumin excretion is low during space mission compared to data on the ground before or after mission. Low urinary albumin excretion could be another effect of exposure to weightlessness (microgravity).
Cirillo
Massimo
M
Nephrology, Second University of Naples, Naples, Italy.
De Santo
Natale G
NG
Heer
Martina
M
Norsk
Peter
P
Elmann-Larsen
Benny
B
Bellini
Luigi
L
Stellato
Davide
D
Drummer
Christian
C
D000418:Albumins / Q000032:analysis; D000419:Albuminuria / Q000652:urine*; D018480:Astronauts / Q000706:statistics & numerical data*; D004044:Dietary Proteins; D006801:Humans; D008297:Male; D013026:Space Flight / Q000706:statistics & numerical data*; D013997:Time Factors; D014508:Urea / Q000652:urine; D014893:Weightlessness
D000418:Albumins; D004044:Dietary Proteins; D014508:Urea