Arterial blood gases in normal hamsters at rest and during exercise

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Abstract
Arterial blood gases and pH were measured in awake, unrestrained male golden hamsters (Mesocricetus auratus) using a cannula implanted in the aortic arch. Samples drawn on the 4th-15th postoperative day in 21 hamsters disclosed mean .+-. SD values for PaO2 [arterial O2 tension] of 73.5 .+-. 5.1 Torr, for PaCO2 [arterial CO2 tension] of 41.4 .+-. 2.7 Torr, and for pH of 7.46 .+-. 0.03; the calculated HCO3- was 28.8 .+-. 2.7 mmol/l, alveolar PO2 was 100.5 .+-. 3.2 Torr, and alveolar-to-arterial PO2 difference (P(A-a)O2) was 26.9 .+-. 5.0 Torr. The effect of exercise was studied in 8 hamsters during forced running on a horizontal treadmill at a speed of 9.6 m/min. There was no significant difference between values on blood drawn between 30-90 s and between 120-180 s of exercise. During exercise, mean pH was unchanged from resting values; PaO2 (mean .+-. SD) rose 12.9 .+-. 7.9 Torr, PaCO2 decreased 6.6 .+-. 2.6 Torr, PAO2 rose 7.9 .+-. 3.2 Torr, and HCO3- decreased 3.5 .+-. 2.3 mmol/l (P < 0.01). The P(A-a)O2 decreased in 6 of the 8 animals during exercise. PaO2 increased during exercise because of increased alveolar ventilation and narrowing of the P(A-a)O2; this narrowing most likely results from the opening of closed airways and reduction in ventilation-perfusion mismatch. This pattern of low PaO2 during rest possibly evolved as an adaptation to the hamster''s fossorial habits.