NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Human skeletal muscle protein breakdown during spaceflightHuman spaceflight is associated with a loss of body protein. Excretion of 3-methylhistidine (3-MH) in the urine is a useful measurement of myofibrillar protein breakdown. Bed rest, particularly with 6 degrees head-down tilt, is an accepted ground-based model for human spaceflight. The objectives of this report were to compare 3-MH excretion from two Life Sciences shuttle missions (duration 9.5 and 15 days, n = 9) and from 17 days of bed rest (n = 7) with 6 degrees head-down tilt. The bed rest study was designed to mimic an actual Life Sciences spaceflight and so incorporated an extensive battery of physiological tests focused on the musculoskeletal system. Results showed that nitrogen retention, based on excretion of nitrogen in the urine, was reduced during both bed rest [from 22 +/- 1 to 1 +/- 5 mg N x kg(-1) x day(-1) (n = 7; P < 0.05)] and spaceflight [from 57 +/- 9 to 19 +/- 3 mg N x kg(-1) x day(-1) (n = 9; P < 0.05)]. 3-MH excretion was unchanged with either bed rest [pre-bed rest 5.30 +/- 0.29 vs. bed rest 5.71 +/- 0.30 micromol 3-MH x kg(-1) x day(-1), n = 7; P = not significant (NS)] or spaceflight [preflight 4.98 +/- 0.37 vs. 4.59 +/- 0.39 micromol 3-MH x kg(-1) x day(-1) in-flight, n = 9; P = NS]. We conclude that 1) 3-MH excretion was unaffected by spaceflight on the shuttle or with bed rest plus exercise, and 2) because protein breakdown (elevated 3-MH) was increased on Skylab but not on the shuttle, it follows that muscle protein breakdown is not an inevitable consequence of spaceflight.
Document ID
20040172986
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Stein, T. P.
(School of Osteopathic Medicine, University of Medicine and Dentistry of New Jersey Stratford 08084, United States)
Schluter, M. D.
Date Acquired
August 22, 2013
Publication Date
April 1, 1997
Publication Information
Publication: The American journal of physiology
Volume: 272
Issue: 4 Pt 1
ISSN: 0002-9513
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
STS-58 Shuttle Project
manned
long duration
STS-40 Shuttle Project
short duration
Non-NASA Center
Skylab Project
NASA Discipline Musculoskeletal
Flight Experiment

Available Downloads

There are no available downloads for this record.
No Preview Available