Abstract: Objective: To observe the effects of repeated horizontal -Gx acceleration exposure on cardiac structure in New Zealand rabbits. Methods: Twenty New Zealand rabbits were divided into 2 groups (n=10): control group and -Gx acceleration exposure group. The rabbits in -Gx acceleration exposure group were exposed to -3. 6 Gx with 2 s, at intervals of 5 min, repeated 20 times daily, with a total of 30 d; the control group didn't undergo the acceleration stress. After the last -Gx acceleration exposure, the animals were killed by intravenous injection of air, and two small pieces of myocardium were immediately dissected from the left ventricles for structure examination using optical microscope and transmission electron microscope. Results: There was no significant difference in the myocardial cell morphology and arrangement observed under the optical microscope between the -Gx acceleration exposure group and the control group; the myocardial fibers arranged in disorder, myocardial cell edema, nuclear membrane expansion, vascular endothelial basement membrane separation were observed in the -Gx acceleration exposure group under transmission electron microscope, compared with the control group. Conclusion: -Gx acceleration exposure can lead to ultrastructural damage in rabbit cardiac myocytes. It suggested that the more attention should be paid to the effect and protection of long-term horizontal -Gx acceleration exposure on the cardiac function of carrier fighter pilots.

Key words: acceleration, myocardial cell, electron microscopy, cytopathology, rabbit