Haemodynamic changes caused in rats by prolonged accelerations

Experiments were performed on 60 rats undergoing about 5 Gz acceleration. The animals were killed in liquid nitrogen at various times after centrifugation (time of centrifugation 1 hour). Before centrifugation 131I-labelled albumin was injected intravenously and after the experiment radioactivity of muscles from the extremities was measured. The following conclusions were drawn from the experiments: (i) About 5 Gz acceleration in the longitudinal axis results in blood displacement to the hind limbs with extravascular leakage of albumin. (ii) Immediately after centrifugation lowering of blood amount in the hind limbs occurred. During the first 15 minutes this decrease progresses very quickly, while later it is much smaller. Nevertheless even 3 hours after centrifugation there was only partial return to normality. (iii) Transudation of albumin in the hind limbs lasts a few hours after centrifugation. (iv) The haemodynamic changes caused by centrifugation consist of blood stasis and extravascular leakage of proteins.