EFFECTS OF 1-MONTH AND 6-MONTH SPACEFLIGHT ON BONE MASS AND BIOCHEMISTRY IN 2 HUMANS

The bone mineral density and the biochemical parameters exploring bone cell activities were analyzed in two cosmonauts who spent 1 and 6 mon ths, respectively, in the Russian MIR station, Measurements were perfo rmed before the flight, after the flight, and after a recovery period, At the end of the first month, peripheral QCT measurements indicated a slight decrease of trabecular bone mass in the distal tibial metaphy sis, However, after 6 months of spaceflight, a more marked loss of tra becular and cortical bones was observed in the tibia, and was still si gnificant after 6 month recovery in the trabecular compartment, wherea s a decrease was no longer observed in the cortical envelope, No chang e was observed in either compartment of the distal radius at any time, Ultrasound BUA of the calcaneus was greatly reduced by the first mont h, followed by a more dramatic decrease after month 6, Ultrasound SOS detected no change, Parameters reflecting bone formation activity appe ared to be depressed after both missions, In contrast, no dramatic cha nge in resorption parameters was observed, except for a trend toward a n increase in pyridinoline. In conclusion, the lower weight-bearing bo nes appeared more sensitive than the upper ones in terms of spacefligh t-induced bone loss, This probably explained the absence of marked sys temic biochemical data changes, This study further suggests that recov ery in the tibial trabecular compartment 6 months after landing was no t completed after a 6 month mission. (C) 1997 by Elsevier Science Inc.