Hypertension induced by repeated exposure to high sustained +Gz (HS + Gz) stress

The purpose of this study was to determine whether repeated exposure to high sustained +Gz (HS + Gz) stress induced persistent changes in the functional state of the cardiovascular system. Three groups of rabbits--centrifuged, restrained, and control--were studied. After being placed in the restraining system of the centrifuge, the animals were submitted three times in a row to 8-9 +Gz sustained for 40 s. This exposure was repeated three times a week for 3-6 weeks. Restrained animals were not exposed to HS + Gz. Control animals were not restrained. The two types of stress (centrifuge + restraint; restraint alone) determined the appearance of two types of arterial hypertension. Systolic arterial pressure (AP) and left ventricular pressure (LVP) significantly increased in restrained animals. The function of the cardiovascular system was more perturbed in centrifuged rabbits since the significant changes affected not only systolic AP and LVP but alos systemic diastolic AP and the maximum rate of rise of LVP. The myocardium of rabbits repeatedly subjected to HS + Gz exposures, except for those that suffered a fracture of the lumbar spine, was significantly glycogen-depleted.