Levels of PO2, oxygen saturation, hematocrit, lactic acid, pH, H+, PCO2 and HCO3− in arterial blood of ground squirrels. (A) Arterial blood oxygen partial pressure (PO2), (B) arterial blood oxygen saturation, (C) arterial blood hematocrit, (D) arterial blood lactic acid (LaC), (E) arterial blood partial pressure of carbon dioxide (PCO2), (F) arterial blood HCO3−, (G) arterial blood pH, (H) arterial blood H+. SA: summer active, LT: late torpor, IBA: interbout arousal, n = 3~6. Data are mean ± SD. Statistically significant differences are denoted as follows: * p < 0.05, ** p < 0.01, *** p < 0.001, as compared with the SA group, and ## p < 0.01, ### p < 0.001, as compared with the LT group.