Liver Regeneration in Rats Exposed to Simulated Changes in Gravity

Abstract

Summary

Partial hepatectomies were performed on 7-week-old male Sprague-Dawley rats that were subsequently centrifuged at 2.5 g or 4.7 g and sacrificed at various postoperative time intervals. No liver regeneration as measured by the mitotic index was noted in rats centrifuged at 2.5 g, 24 hours after operation; at this time period the control rats at normal gravity showed initiation of mitotic activity. At the 28-hour period, regeneration at 2.5 g was noted but the value was significantly lower than that of controls. The initiation of mitosis was delayed even longer in the group of animals that was centrifuged at 4.7 g.

To study the effects on liver regeneration of a decrease in gravity, 3-week-old weanling rats were centrifuged for 4 weeks at 4.7 g, removed from the centrifuge, hepatectomized, and sacrificed 24, 28, and 36 hours after partial hepatectomy. Greater mitotic activity was observed in the 4.7 g-conditioned rats than in the rats not exposed to centrifugation during all 3 postoperative time periods. Thus, the onset of mitosis is delayed in rats exposed to increased gravity and mitosis is enhanced in rats conditioned to increased gravity when they are subsequently returned to normal gravity.