Submitted on May 25, 2007
Accepted on July 18, 2008
A NON-INVASIVE ANALYSIS OF URINARY MUSCULOSKELETAL COLLAGEN METABOLISM MARKERS FROM RHESUS MONKEYS SUBJECT TO CHRONIC HYPERGRAVITY
Daniel Anthony Martinez1*, Patricia E Patterson-Buckendahl2, Andrew Lust3, Kelly M Shea-Rangel3, Tana M. Hoban-Higgins4, Charles A. Fuller5, and Arthur C. Vailas6
1 Biomedical Engineering Program, University of Houston, Connective Tissue Physiology Laboratory, N207 D Engineering Bldg. 1, Houston, Texas, 77204-4006, United States; Health and Human Performance, University of Houston, 3855 Holman St. GAR 104, Houston, Texas, 77204-6015, United States
2 Center of Alcohol Studies, Rutgers University, Piscataway, New Jersey, United States
3 Biomedical Engineering Program, University of Houston, Connective Tissue Physiology Laboratory, N207 D Engineering Bldg. 1, Houston, Texas, 77204-4006, United States
4 Neurobiology, Physiology and Behavior, University of California at Davis, Davis, California, United States
5 Section of NPB, University of California, Davis, California, United States; Neurobiology, Physiology and Behavior, University of California at Davis, Davis, California, United States
6 Office of the President, Idaho State University, Pocatello, Idaho, United States
* To whom correspondence should be addressed. E-mail: ddam{at}uh.edu.
A decrease in load bearing activity as experienced during spaceflight or immobilization affects the musculoskeletal system in animals and humans, resulting in the loss of bone and connective tissue. It has been suggested that hypergravity can counteract the deleterious effects of microgravity induced musculoskeletal resorption. However, little consensus data has been collected on the non-invasive measurement of collagen degradation products associated with enhanced load bearing stress on the skeleton. The purpose of this study is to assess the urinary collagen metabolic profiles of rhesus monkeys (Macaca mulatta) during: 1) two weeks basal 1G (pre-HG), 2) two weeks of HG (2G) and 3) two periods of post-HG recovery (1G). Twenty-four hour urine collections were obtained from six individual rhesus monkeys. Hydroxyproline (Hyp) and collagen cross-links (HP and LP) were measured by rp-HPLC. Urine calcium, measured by atomic absorption, and creatinine were also assayed. The results indicate no changes in non-reducible cross-links and Hyp during the hypergravity period. Collagen cross-link biomarker levels were significantly elevated during the second week of the post-HG period. Urine calcium content was significantly lower during HG compared to 1G control levels, suggesting calcium retention by the body. We conclude that there is an adaptation of the non-human primate musculoskeletal system during hyperloading and that non-invasive measurements of musculoskeletal biomarkers can be used as indicators of collagen and mineral metabolism during hypergravity and recovery in non-human primates.
