Renal responsiveness to aldosterone during exposure to simulated microgravity
1 U.S. Army Institute of Surgical Research, Fort Sam Houston; 2 Department of Exercise Science, University of Utah, Salt Lake City, Utah 84103; 3 U.S. Army Medical Department and School, Department of Veterinary Medicine, Fort Sam Houston, Texas 78234; 4 Department of Mathematical Sciences, Univ...
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Veröffentlicht in: | Journal of applied physiology (1985) 2000-11, Vol.89 (5), p.1737-1743 |
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Zusammenfassung: | 1 U.S. Army Institute of Surgical Research, Fort Sam
Houston; 2 Department of Exercise Science, University of Utah,
Salt Lake City, Utah 84103; 3 U.S. Army Medical Department and
School, Department of Veterinary Medicine, Fort Sam Houston, Texas
78234; 4 Department of Mathematical Sciences, University of
North Carolina, Greensboro, North Carolina 27412; and 5 Life
Science Division, NASA-Ames Research Center, Moffett Field, California
95070
We measured renal functions and
hormones associated with fluid regulation after a bolus injection of
aldosterone (Ald) during head-down tilt (HDT) bed rest to test the
hypothesis that exposure to simulated microgravity altered renal
responsiveness to Ald. Six male rhesus monkeys underwent two
experimental conditions (HDT and control, 72 h each) with each
condition separated by 9 days of ambulatory activities to produce a
crossover counterbalance design. One test condition was continuous
exposure to 10° HDT; the second was a control, defined as 16 h
per day of 80° head-up tilt and 8 h prone. After 72 h of
exposure to either test condition, monkeys were moved to the prone
position, and we measured the following parameters for 4 h after
injection of 1-mg dose of Ald: urine volume rate (UVR); renal
Na + /K + excretion ratio; renal clearances of
creatinine, Na + , osmolality, and free water; and
circulating hormones [Ald, renin activity (PRA), vasopressin (AVP),
and atrial natriuretic peptide (ANP)]. HDT increased
Na + clearance, total renal Na + excretion, urine
Na + concentration, and fractional Na +
excretion, compared with the control condition, but did not alter plasma concentrations of Ald, PRA, and AVP. Administration of Ald did
not alter UVR, creatinine clearance, Ald, PRA, AVP, or ANP but reduced
Na + clearance, total renal Na + excretion,
urinary Na + /K + ratio, and osmotic clearance.
Although reductions in Na + clearance and excretion due to
Ald were greater during HDT than during control, the differential
(i.e., interaction) effect was minimal between experimental conditions.
Our data suggest that exposure to microgravity increases renal
excretion of Na + by a natriuretic mechanism other than a
change in renal responsiveness to Ald.
bed rest; natriuresis; renal function; plasma renin activity; antidiuretic hormone; atrial natriuretic peptide |
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ISSN: | 8750-7587 1522-1601 |
DOI: | 10.1152/jappl.2000.89.5.1737 |