ABSTRACT
<p><b>OBJECTIVE</b>To study the effect of microfilament cytoskeleton changes induced by simulated microgravity on the NO/NOS system of osteoblasts, and explore the mechanism of weightlessness leading to osteoporosis.</p><p><b>METHODS</b>Mouse osteoblast-like cell line MC3T3-E1 were divided into simulated microgravity (by rotating clinostat) group, 0.5 microg/ml cytochalasins B group, simulated microgravity+cytochalasins B group, and normal gravity group. After cell culture for 48 h with corresponding treatments, immunofluorescence staining of the cells by FITC-phallacidin was performed to observe the changes of microfilament under laser confocal microscope. NOS activity of the cells was tested with NOS detection kit, and the NO concentration in the cell supernatant was measured with nitrate reductase method.</p><p><b>RESULTS</b>Depolymerization of the microfilament cytoskeleton with irregular arrangement and reduced tension fibers occurred in the cells except for those in the normal gravity group, which was especially obvious in the microgravity+cytochalasins B group. Compared with the normal gravity group, the cells in the other groups showed increased iNOS activity and NO concentration but decreased eNOS activity, especially obvious in simulated microgravity+ cytochalasins B group.</p><p><b>CONCLUSION</b>Disruption of the microfilament cytoskeleton induced by simulated microgravity can regulate the NO/NOS system to influence the signal transduction of the osteoblasts.</p>