The absence of erythrocytic dehydration activity in whole tadpole blood is thought to be due to a specific property of plasma that either inhibits HCO₃⁻ flux across the red cell membrane or inhibits carbonic anhydrase (CA) directly. Removal of plasma and resuspension of intact tadpole (Rana catesbiana) erythrocytes in physiological saline resulted in a marked catalysis of the dehydration reaction as measured manometrically. Acceleration of the rate of H₂CO₃ dehydration was also observed when whole tadpole blood was lysed (the plasma being present) and when washed cells were lysed and assayed (the plasma being absent). CA activity was demonstrated in RBC cytoplasm but was not evident in extracted RBC membranes, blood plasma and gill filaments. In aquatic tadpole blood CA activity was found to be 4-5 times lower than that observed in the terrestrial adult toad (Bufo marinus). The functional significance of CA during metamorphosis is discussed.
Alison Elizabeth Parker (Tue,) studied this question.
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