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THERE seems at present to be no general agreement amongst workers on liver catalase concerning either the best method of estimating the enzyme, or of preparing the homogenates in which the enzyme is measured. It is well known that the results of catalase activity measurements are considerably affected by such variables as temperature, hydrogen peroxide concentration, length of time for which the enzyme and substrate are allowed to remain in contact, and whether the measurements are of oxygen evolution or hydrogen peroxide disappearance. However, little attention seems to have been paid to the possibility that some discrepancies in the results obtained by various authors may depend as much on the method by which liver homogenates are prepared as on the method of enzyme assay. An example of an apparently complete disagreement in the literature concerns the question of a sex difference in liver catalase activity in mice and rats. Adams (1950, 1952) reported that a sex difference was present in the livers of the hetero-genous strains of mice used, the catalase level in males being higher than in females. Hargreaves and Deutsch (1952) found similar results in their rats. However, Day, Gabrielson, and Lipkind (1954) measured liver catalase activities in both sexes of six pure line strains of mice and stated that the male level exceeded the female in only one strain. In three other strains there was no particular sex difference, and in the remaining two the female level was higher than the male. In view of these results Adams (1956) measured catalase activities in the livers of 14 strains of mice (including 10 pure lines) and three pure line strains of rats. All the rats, and all the mice with the exception of the related C57 black and brown strains, had significantly higher liver catalase activities in males than in females. The C57 black strain was stated by Greenstein and Andervont (1942) to be exceptional in that (a) the liver catalase activity was insensitive to S37 tumour growth, and (b) the activity was only about half that of the other strains studied. Adams (1956) found the catalase level in the C57 strains to be about half that of the other strains, in agreement with Greenstein and Andervont (1942). However, Day et al. (1954) stated that the catalase activity of their C57 brown mice was high, and equal to that of the other strains used. They also stated that …

The Effect of the Degree of Homogenization on the Catalase Activity of Liver “Homogenates”