BRAIN CARBONIC ANHYDRASE: ACTIVITY IN ISOLATED MYELIN AND THE EFFECT OF HEXACHLOROPHENE

Abstract

Abstract— Animals receiving hexachlorophene (HCP) in their diet develop cerebral edema with vacuolation of the myelin sheath. When carbonic anhydrase activities were measured in homogenates of brains from HCP‐fed and control rats, the HCP‐fed rats showed small decreases in the enzyme activity, but these changes were not statistically significant. HCP did inhibit the enzyme in vitro but at higher concentrations (10 −5 ‐10 −4 m ) than have been reported for HCP levels in brains of experimental animals. Carbonic anhydrase activity was present in myelin preparations obtained by gradient centrifugation and osmotic shock or by subcellular fractionation. When the latter procedure was used, myelin carbonic anhydrase had a specific activity which was higher than that of the mitochondrial fraction. The myelin enzyme was inhibited by 10 −9 10 −8 m ‐acetazolamide and, like the homogenates and the commercial enzyme, was inhibited by HCP. The mechanism for HCP toxicity remains unknown, but this study does suggest that carbonic anhydrase is an intrinsic component of the myelin sheath.