Blood volume responses of rats adppted to different barometric pressures (38482).

The total blood volume, circulating red cell volume (CRCV), and plasma volume of rats exposed for 30 days to either 480 or 380 mmHg were quite different. At the lower altitude 480 mmHg) total blood volume was similar to that found in sea level controls of a similar weight and age, while CRCV was increased and plasma volume was decreased. However, at the higher altitude CRCV was increased to a much greater extent, with the result that the total blood volume was approximately 44% greater than at 480 mmHg. The differences in response to the two barometric pressures became even more striking when the rats adapted to 380 mmHg were compared with their age- and weight-matched controls. Diet restrictions in the absence of hypoxia resulted in significant decreases in CRCV, plasma volume, and total blood volume. Consequently, when compared to these animals, rats adapted to 380 mmHg had a 100% greater total blood volume due primarily to a higher CRCV, but also to a higher plasma volume.