Abstract
Introduction: We have developed a bone loss countermeasure program for Japanese astronauts with the aid of the Bone Loss Countermeasure Advisory Working Group. Pharmacological intervention (Bisphoshonate administration) is planned for astronauts with osteoporosis BMD (T-score <2.5) as treatment, and for astronauts with osteopenia BMD (T-score -2.5 to-1.0) as preventive therapy for long duration space flight. To validite this program, JAXA participated in the long duration bed rest study at MEDES, co-sponsored by European and French Space Agencies.
Methods: Twenty-five male volunteers were split into three groups: control (9 subjects), drug (7), and exercise (9) groups. Bisphosphonate was infused intravenously 14 days before the bed rest. Data collection including BMD, urinary Ca excretion, abdominal X-P for renal stone was performed 15 days before, during 90-day head-down tilt bed rest, and up to one year after bed rest.
Results: DXA results showed the BMD of total femoral bone decreased by 6.2% in the control group and by 3.6% in the exercise group, while pharmacological group showed no change at the end of 3-month bed rest period. Urinary Ca excretion significantly increased in the control group and in the exercise group during bed rest. In the pharmacological group, urinary Ca excretion decreased immediately after infusion, and stayed low for one month. Moreover, existence of renal calculi was detected on the plain abdominal X-ray after bed rest, in two from the control group and four from the exercise group, but none from the pharmacological group. [Jpn J Physiol 54 Suppl:S46 (2004)]
