Effects of hypoxia on acid‐base balance, blood gases, catecholamines, and cutaneous ion exchange in the larval tiger salamander (<i>Ambystoma tigrinum</i>)

Abstract

Abstract The effects of hypoxia on acid‐base balance and blood gases were examined in larval Ambystoma tigrinum . Environmental hypoxia (P = 24 mm Hg) resulted in a severe metabolic acidosis. During approximately 4 hr of hypoxia, arterial P fell from 23 to 8 mm Hg while P did not change; plasma lactate concentrations rose from 1.7 to 11 mM; pH fell from 7.9 to 7.3 and [HCO 3 − ] decreased by 8.2 mM. After restoration of normoxia, P rose to 40 mm Hg within 1 hr. All variables returned to control levels between 4 and 24 hr. Circulating levels of norepinephrine were significantly increased and highly correlated with pH after 4 hr of hypoxia. Net and unidirectional Na + and Cl − flux rates were measured before, during, and after hypoxia to determine if cutaneous ion exchange is associated with the acid‐base disturbance. Neither Na + nor Cl − flux rates changed significantly during hypoxic exposure or recovery.