| The Plateau zokor (Myospalax baileyi) and plateau pika (Ochotona curzniae) are species endemic to the Qinghai-Tibet Plateau.To study the adaptive characteristics of pulmonary acinus structure in the two species, we measured relative indices by using stereological methods, using the SD rats as control model. The results revealed evident difference in lung weight vs. body weight (LVB) between the three species. The LVB value was the highest in plateau zokors, and lowest in SD rats. There was no significant difference in density of pulmonary alveoli (DPA) between plateau zokors and plateau pikas, but the DPAs in the two species were higher than that in SD rats. The aera of pulmonary alveolous (APA) and elastic fiber vs. lung parenchyma (EVP) of plateau zokors and plateau pikas were significantly lower than that of SD rats. It was obviously different among thickness of interalveolar septum (TIS) of the three animals. Air-blood barrier arithmetic mean thickness (Ta) and harmonic mean thickness (Th) were both less than those in SD rats. The muscle thickness vs. the outer diameter of microvessel (MVM) and microvessel density (MVD) of plateau zokors and plateau pikas were significantly higher than those in SD rats, and there was obviously different in MVM between the two high altitude animals.To explore the adaptive mechanisms of blood in plateau zokor and plateau pika to the hypoxic environment, the blood-gas propoties, blood indices, content of lactic acid and activity of latate dehydrogenase were analyzed, meanwhile, the types of hemoglobin and lactate dehydrogenase (LDH) were analyzed by polyacrylamide gel electrophoresis. The results indicated that it was significantly different in arterial blood pH of plateau zokor with plateau pika and SD rat, but no different in venous blood pH. The partial pressure for carbon dioxide (PCO2) in arterial and venous blood of plateau zokor was the highest, and the difference of PCO2 was also higher. The partial pressure for oxygen (PO2) in arterial blood of plateau zokor was the highest, and lowest in venous blood. The difference of PO2 in arterial blood to venous blood of plateau pika was higher than that of SD rat, too. The difference of oxygen saturation in arterial blood to venous blood of the two high-altitude animals were obviously higer than that of SD rat, but that of plateau zokor was the highest. It was not significantly different in red blood corpuscle count (RBC), hematocrit (HCT), and mean corpuscular volume (MCV) between plateau zokors and plateau pikas, but the RBC of the zokors and the pikas were significantly higher, and the HCT and MCV were significantly lower than those in SD rats. The hemoglobin concentration (HBC) in plateau pikas was significantly lower than that in plateau zokors and SD rats. Two types of hemoglobin were discovered in plateau zokors, three types of hemoglobin in plateau pikas, five types of hemoglobin in SD rats. The hemoglobin types of the two high altitude animals demonstrated convergent evolution characteristics according to the electrophoresis migration, and it showed significant difference with SD rats. The activity of LDH and content of lactic acid (LD) in plateau pika were the highest, and that in plateau zokor were the lowest. Five types of LDH isozymogram in plateau zokor were discovered, LDH-M was in major, and six types in plateau pika, LDH-H was in major.In conclusion, the structures of pulmonary acinus and blood characteristics in two high altitude animals show obvious convergent evolution in long time of adapting the hypoxic environment, that make lung have strong capacity of oxygen uptake, and permit blood to have strong capacity to carry oxygen and release more in tissues. However, they have significant difference in some indices, maybe they due to the different habitats and habits.
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