[Variation of several volume regulating hormones during 21 d - 6 degrees head-down bed rest].
Objective To investigate variations of plasma renin activity, a prostaglandin I2 (PGI2) during 21 d -6 degrees head-down tilt (HDT) with and without lower body negative pressure (LBNP).


METHODS
-6 degrees head-down tilt for 21 d were used to simulate weightlessness. 12 healthy male, aged 23.7 +/- 5.0, were equally and randomly divided into control group (CON) and LBNP group. The latter subjected to LBNP (-30 mm Hg, 1 h/d) in the last week of HDT. Samples of plasma were taken before HDT and on the 2nd, 4th, 11th and 22nd day during HDT.


RESULTS
Compare to control levels, Ald declined significantly on the 2nd (CON -30%, P < 0. 05; V. S. LBNP -38%, P < 0.01), and increased significantly on the 11th day (CON +30%, P < 0.05; LBNP +48%, P < 0.01). PRA reached peak value on the 4th day (P < 0.05), and declined to below the control level on the 22nd day. PGI2 increased constantly during HDT, and increased significantly on the 22nd day (CON P < 0.01), 11th, 22nd (LBNP P < 0.05). No apparent difference was found between groups after LBNP concerning PRA and Ald; and PGI2 didn't increase further in LBNP group. Conclusion HDT induced a timely increasing in PRA and Ald, constant increasing in PGI2.
Cao
X S
XS
Department of Aviation Medicine, The Fourth Military Medical University, Xi'an, China.
Wu
X Y
XY
Jiang
C L
CL
Sun
X Q
XQ
Jiang
S Z
SZ
Yao
Y J
YJ
D000222:Adaptation, Physiological / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D000337:Aerospace Medicine; D000450:Aldosterone / Q000097:blood / Q000378:metabolism; D001510:Bed Rest; D011464:Epoprostenol / Q000097:blood / Q000378:metabolism; D018475:Head-Down Tilt; D006801:Humans; D008150:Lower Body Negative Pressure; D008297:Male; D012083:Renin / Q000097:blood / Q000378:metabolism; D012084:Renin-Angiotensin System / Q000502:physiology*; D013997:Time Factors; D018474:Weightlessness Simulation
D000450:Aldosterone; D011464:Epoprostenol; D012083:Renin