Esterase substrate specificity in the testis of the growing mouse

The age distribution of esterases in the interstitial cell of the mouse testis was studied between birth and the end of the tenth week of postnatal life by using the substrates O-acetyl-s-bromoindoxyl, a-naphthyl acetate, naphthol AS acetate, naphthol AS-LC acetate, and naphthol AS-D acetate. With indoxyl acetate, esterase activity is prominent at birth and wanes over the first 2 weeks of postnatal life. Esterase activity with the substrates a-naphthyl acetate, naphthol AS acetate, and naphthol AS-LC acetate is first demonstrable 2, 3, and 7 weeks after birth respectively, and in each instance increases steadily with age. Differences in the volume of reactive interstitial tissue for each of these substrates are •demonstrable at all ages. Naphthol AS-D acetate is only utilized by the interstitial cells of the 10-week mouse. No esterase substrate is used by all age groups, and quantitative differences at a given age exist between the individual substrates. These results are thought to imply the existence of at least 5 substrate-specific esterases in the mouse interstitial cell, and their possible relation to steroid synthesis is noted.