title: Responses of blood volume and red cell mass in two strains of rats acclimatized to high altitude.
abstract: Two strains of rats, one that adapts successfully to high altitude (HA) (Madison = M) and the other that adapts poorly and suffers a high mortality rate at high altitude (Hilltop = H) were studied during 40 days of exposure to a simulated altitude of 18 000 ft (5450 m; PB = 175). The time rate of change of blood volume (TBV), red cell volume (RBCV), plasma volume (PV) and hematocrit (Hct), and the interrelationships of these variables, particularly emphasizing TBV, PV and Hct as functions of RBCV, were compared in the M and H strains. Sea level control values in the two strains were not different, but by the 5th day at HA RBCV and TBV had expanded to a greater extent in H than M - a difference that was maintained throughout the 40 days - but PV decreased similarly in the two strains. By 30 days the inter-strain differences of RBCV, TBV, and Hct became more pronounced but still no difference of PV was noted. The most significant feature was the greater polycythemic response of H, which at the extreme range was not associated with any further decrease of PV and therefore resulted in rapid expansion of TBV. The probable effects of these responses on cardiovascular function and oxygen transport are discussed, comparing the differences of H and M strains, which became maladaptive in H. The similarity of the responses in H to those of man with chronic mountain sickness is noted.
mesh_terms: D000222:Adaptation, Physiological; D000531:Altitude; D000818:Animals; D001810:Blood Volume; D004906:Erythrocyte Count; D004912:Erythrocytes / Q000166:cytology*; D006400:Hematocrit; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains / Q000502:physiology*; D013045:Species Specificity