Interactive effects of nutrition, environment, and rat-strain on cortical and vertebral bone geometry and...

Because of differences between rodent experiments on USSR and USA spaceflights, the present experiment was designed to generate comparative data about the sensitivity of cortical (humerus) and vertebral (T7) bones to cage environment, diet, and rat-strain differences. For 2 weeks (48-62 d), male Taconic-Sprague-Dawley and Czechoslovakian-Wistar rats were maintained in flight-simulation cages (1 rat/cage = USA, 10 rats/cage = USSR) and fed either USSR or USA diets. All rats increased (greater than 60%) their body mass during the two weeks, and there were no differences among humeral lengths for the different groups. Rats in USSR cages had significantly larger total and medullary cross-sectional areas for the humerus, and the cross-sectional areas of T7 of Taconic rats were greater than the Czech rats. USSR caging resulted in significantly enhanced structural and material properties in rat humeri, while the USA diet produced significantly greater humeral maximum and failure loads. The flexural rigidity of the Czech-rat humeri was significantly greater than the Taconic rats. Humeri from Czech rats on the USA diet had significantly greater material properties in the elastic-loading region than did Taconic rats on the USSR diet. Further, the humeral failure loads of Taconic rats on the USSR diet were more adversely affected by USA cages than were the Czech rats on the USSR diet. In T7 vertebrae, no significant structural differences were found among the groups, but material properties were influenced by all three factors; generally, the combination of factors that produced the significantly greater T7 material properties was: USSR caging, USSR diet, and the Czech strain of rat.