To assess the effects of mechanical stress on bone mineral density in stroke-prone spontaneously hypertensive rats (SHRSP), ten-week-old SHRSP were assigned to a jump exercise (SHR-E, n=11) or a sedentary group (SHR-S, n=11). Normotensive Wistar-Kyoto rats (WKY) were also assigned to a jump exercise (WKY-E, n-11) or sedentary group (WKY-S, n=11). Rats in the exercise groups jumped 10 times/day, 5 days/wk, for 6 weeks, with a jumping height of 40 cm. After the experiment, the bone mineral density of dissected left tibia was measured using dual energy X-ray absorptiometry. There were no significant differences in final body weight or systolic blood pressure between either the SHR-E and SHR-S or the WKY-E and WKY-S. Tibial bone mineral density was greater in SHR-E (+4.1%, P<0.05) than in SHR-S, and in WKY-E (+5.8%, P<0.01) than in WKY-S. Tibial bone mineral content was also greater in SHR-E (+10.0%, P<0.01) than in SHR-S, and in WKY-E (+6.5%. P<0.05) than in WKY-S. From these results, we conclude that, despite their abnormal calcium metabolism, the bones of SHRSP have the potential to increase bone mineral density by adapting to jump exercise as same as the bones of WKY
