Acclimatization of newborn rats and guniea pig to 3000 to 5000 m stimulated altitudes

Abstract

Two species of newborn rodents (guinea pigs and rats) were acclimatized to simulated altitudes of 3000 to 6000 m during 2 to 8 weeks after birth. Both weight increase was significantly retarded in both species at altitudes of 5000 m and higher. Heart weight relative to body weight increased by 50% at 3000 m and 30% at 5000 m (after 7 weeks) in rats but was only 17% increased even at 5000 m (6 weeks) in guinea pigs. Relative lung weights increased by 40% at 3000 m in rats and 500 m in guinea pigs; at 5000 m rats showed a 13% increase. Hb-concentration increase (20%) was not significantly different in rats at 3000 m and 5000 m, respectively, in guinea pigs it was below 10% at 3000 m and around 40% at 500 m. Half saturation pressures of blood (P 50) increased in rats significantly compared to controls but not in guinea pigs. The results suggest that relative maturity and high blood oxygen affinity in newborn guniea pigs favor high altitude acclimization. Immaturity of newborn rats, their low blood oxygen affinity and immature enzyme patterns are considered as reasons for the smaller resistance against high altitude stres compared to guinea pigs.