EFFECTS OF SPACEFLIGHT ON BONE MINERALIZATION IN THE RHESUS-MONKEY

We combined dual-photon absorptiometry, iliac crest histomorphometry, and backscattered electrons analysis to characterize hone mineralizati on effects of a spaceflight on young monkeys. Two 4- to 5-kg male rhes us monkeys (Macaca mulatta) were flown during a 11.5-day spaceflight t hat took place onboard Cosmos 2229 biosatellite (Bion 10). Vivarium (n = 4) and Earth-based chair (n = 4) control situations were studied fo r comparison. Flight monkeys exhibited lower values of iliac cancellou s bone volume, associated with nonsignificantly thinner trabecular. Bo ne mineralization rate and the proportion of trabecular bone surface i nvolved in mineralization processes were found markedly reduced after spaceflight. Analysis of embedded sections by backscattered electrons imaging showed a nonsignificant shift to lower mineralization in tile Right biopsies vs. postflight mock-up biopsies. These results were in accordance with dual-photon absorptiometry evaluations showing a tende ncy for decreased bone mineral content during flight and recovery ther eafter. The ground simulation experiment performed on tile same monkey s more than 1 mo after landing suggests that the observed effects were specifically related to spaceflight and that the animals had only par tially recovered. Additional animals on future flights will be require d to confirm these findings.