Abstract

Renal carbonic anhydrase from the dog and rat is found chiefly in the supernatant fraction. Based on molar activity and inhibition kinetics, the cytoplasmic enzyme has properties closely akin to the human red cell fraction C, which may be taken as a prototype for most vertebrate tissue and red cell enzymes. The data show that acetazolamide and allied drugs can readily inhibit >99% of cytoplasmic enzyme in vivo at low (5-20 mg/kg) doses. A smaller but definite concentration of enzyme is found in microsomes; on the basis of present criteria this enzyme is different from that of the supernatant. Although somewhat higher concentrations of drugs are necessary for inhibition of microsomal enzyme, these are still within the range attainable in vivo. Physiological manifestations of the system are discussed.