Carbonic anhydrase in the central nervous system of the developing fetus.

Well defined patterns of quantitative distribution of carbonic anhydrase have been reported in the central nervous system of man and of animals (1,2). Two reports have been made on deviations from the normal pattern of distribution in man incident to mental disease (3,4). As part of an effort to elucidate the significance of this enzyme in the central nervous system, a study of its fetal distribution was undertaken. Studies by various workers have been reported on oxygen uptake and on increase in individual enzymes with maturation of the central nervous system. These were made both upon the young of animals immature at birth and upon fetuses of species comparatively mature when born. Measurements of 02 uptake by the central nervous system in puppies from birth to 7 weeks of age, made by Himwich and Fazekas (5), show an increase in metabolic rate proceeding from the medulla to the caudate nucleus and approaching the pattern of the adult in which the respiratory metabolism is found to be higher in the newer phylogenic layers than in the older. Adult oxygen consumption was not attained. Similar findings are reported by Tyler and van Harreveld for therat (6). Studies on the distribution of the enzymes choline esterase, cytochrome oxidase, succinic dehydrogenase, and succinic oxidase show a similar rostra1 movement in attainment of maximum content. In the human fetus obtained by hysterotomies and hysterectomies Youngstrom (7) reports a rapid increase in choline esterase content of the cord, medulla, and midbrain from the 56th to the 121st day of fetal age. In the basal ganglia and cerebrum there was a slight increase up to 4 months, when a precipitous increase occurred. A similar study was made by Nachmansohn (8) in fetal goats. Flexner, Flexner, and Straus (9, 10) studied the increases, in the cerebral cortex only, of cytochrome oxidase, succinic dehydrogenase, and succinic oxidase with growth of the fetal pig. Between the 60th day and birth at 114 days there were two increases in these enzymes which correlated with morphologic changes in the cortical tissue. Studies by Meldrum and Roughton (11) on the development of carbonic anhydrase in the blood of fetal goats and those of Stevenson (12) on the