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Urinary excretion of LH and testosterone from male rats during exposure to increased gravity: post-spaceflight and centrifugationA dissociation between plasma luteinizing hormone (LH) and testosterone (T) appears to exist during exposure to altered gravity. The pulsatile nature of LH release and the diurnal variability of T secretion may mask or bias the effects of altered gravity on the pituitary-gonadal axis when analyzing plasma concentrations. Therefore, we examined the relationship between the excretion of urinary LH and T in male Sprague-Dawley rats during exposure to increased gravity upon return to Earth following a 14-day spaceflight (n = 6) and by 12 days of centrifugation at 2g (n = 8). Excreted LH and T were elevated on the first 3 days postflight. Excreted T was elevated between Days 1 and 8 of centrifugation; however, excreted LH was reduced on Days 2 and 3 compared with control animals. Excreted LH and T were significantly correlated (R = 0.731 and 0.706, respectively) in postspaceflight and centrifuged animals. Correlation curves had similar slopes (0.0213 and 0.023, respectively), but different y-intercepts (-1.43 and 3.32, respectively). The sustained increase in excreted T during centrifugation suggests that the pituitary-gonadal axis in postspaceflight animals may adapt quicker to increased gravity. The upward shift in the correlation curve exhibited by the centrifuged animals suggests that the sensitivity of LH-induced T release is increased in these animals. The previous dissociation between plasma LH and T during altered gravity was not observed in the present study in which excreted LH and T were measured.
Document ID
20040112748
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Ortiz, R. M.
(NASA Ames Research Center Moffett Field CA United States)
Wade, C. E.
Morey-Holton, E.
Date Acquired
August 21, 2013
Publication Date
October 1, 2000
Publication Information
Publication: Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N. Y.)
Volume: 225
Issue: 1
ISSN: 0037-9727
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
short duration
manned
NASA Discipline Regulatory Physiology
Flight Experiment
STS-58 Shuttle Project
NASA Center ARC

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