To evaluate the possible effect of induced
hypercapnia on anaerobic metabolic rate during
anoxia,
musk turtles (Sternotherus odoratus) were submerged in N2-equilibrated water
at 10 degrees C for 3 days either with (anoxic hypercapnic) or without (anoxic normocapnic) elevated aquatic PCO2 (30-40 Torr). Control animals had access to air
at 10 degrees C. Plasma [
lactate] was significantly higher (P less than 0.01) in the normocapnic [59.4 +/- 7.4 (SD) mM; n = 22] than in the hypercapnic (47.4 +/- 8.5 mM; n = 19) anoxic turtles, although the hypercapnic turtles had lower blood pH (P less than 0.05). Plasma ion concentrations (Na, K, Cl, Ca, and Mg), however, were no different in the two groups, although all values other than Na were different from control. In some of the animals, [
lactate] and [
glycogen] (per g wet wt) of skeletal muscle, heart, and liver were measured in addition to blood
acid-base values and
lactate. Tissue
lactates, although significantly elevated from control, and glycogens, although (with the exception of skeletal muscle) significantly reduced from control, were no different in the two anoxic groups. We suggest that these tissue data are more valid indicators of anaerobic metabolic rate than is plasma
lactate and therefore conclude that induced
hypercapnia does not significantly depress anaerobiosis in
musk turtles
at 10 degrees C.