FUTURE HUMAN BONE RESEARCH IN SPACE

Skylab crewmembers demonstrated negative calcium (Ca) balance reaching about -300 mg/day by flight day 84, Limited bone density (BMD) measur ements documented that bone was not lost equally from all parts of the skeleton. Subsequent BMD studies during long duration Russian flights documented the regional extent of bone loss. These studies demonstrat ed mean losses in the spine, femur neck, trochanter, and pelvis of abo ut 1%-1.6% with large differences between individuals as well as betwe en bone sites in a given individual. Limited available data indicate p ostflight bane recovery occurred in some individuals, but may require several years for complete restoration. Long duration bedrest studies showed a similar pattern of bone loss and calcium balance (-180 mg/day ) as spaceflight, During long duration bedrest, resorption markers wer e elevated, formation markers were unchanged, 1,25 vitamin D (VitD) an d calcium absorption were decreased, and serum ionized Ca was increase d. Although this information is a good beginning, additional spaceflig ht research is needed to assess architectural and subregional bone cha nges, elucidate mechanisms, and develop efficient as well as effective countermeasures. Space research poses a number of unique problems not encountered in ground-based laboratory research. Therefore, researche rs contemplating human spaceflight research need to consider a number of unique problems related to spaceflight in their experimental design . (C) 1998 by Elsevier Science Inc. All rights reserved.