Intracelular and extracellular acid-base and electrolyte status of submerged anoxic turteles at 3°C

Abstract

Specimens of fres water turtles ( Chrysemys picta bellii) were acclimated to 3°C and then submerged in completely anoxic water for time periods of up 12 weeks. Blood withdraw via indewelling arterial catheters was analysed for plasma pH, P CO 2 , bicarbonate concentration, [lactate], [Na +], [K +], [Ca 2+] and [Mg 2+], and tissue samples of skeletal muscle, liver and cardiac muscle were excised. Samples of skeletal muscle were analysed for intracellular pH (DMO), [lactate], [Na +], K +], [Ca 2+], and [Mg 2+], and samples of liver and cardiac muscle for intracellular pH and [lactate] during normoxia and after 1, 2, 4, 8 and 12 weeks of anoxia. Arterial plasma pH fell from 8.0 during normoxia to lower than 7.2 concomitant with a reduction in plasma [HCO 3 −] after 12 weeks of anoxia due to the production of large amounts of lactic acid. The intracellular pH (pH i) of heart muscle and liver dropped in parallell or even more than plasma pH, whereas pH i in skeletal muscle changed less resulting in a ΔpH i/°pH e value of less than 0.6. Intracellular [lactate] and [Ca 2+] increased considerably, but attined concentrations much smaller thatn those observed in the extracellular compartment. The intracellular concentrations of K +, Na + and Mg 2+ were also significantly affected, the changes, however, were small in comparison with those observed for Ca 2+ and lactate concentration. The water distribution between intra- and extracellular compartments remained essentially unaffected by anoxia. It is concluded that the considerable increase in extracellular Mg 2+ and Ca 2+ cannot be the result of release from muscle cells and has to be attributed to release from skeleton and shell. The constant distribution of water between body compartments suggests a similar increase in intracellular osmolarity as observed in the ectracellular space. Since the increase in measured intracellular solutes cannot account for the increase in osmolarity, it is likely that one or several unmeasured solutes increased during anoxia.