Localization of beta-galactosidases and acid phosphatase in the small intestinal wall. Comparison of adult and suckling rat.

Abstract

By horizontal sectioning of fresh frozen pieces of rat intestinal wall different parts of the villi and crypts were isolated. The sections were collected in groups, homogenized and used for enzyme analyses. Single sections for histologic examination were taken before and after each collection. A quantitative comparison of the distribution of the two intestinal β-galactosidases, EC 3.2.1.23 (neutral and acid β-galactosidase), and the acid phosphatase, EC 3.1.3.2, in jejunum and ileum of adult and suckling (12 days old) rats was performed. The neutral β-galactosidase, which corresponds to the enzyme usually called lactase, was always present along the villi with the highest activities in the apical halves of the villi. This distribution profile is typical for digestion enzymes. The acid β-galactosidase, which is chiefly a heterogalactosidase, and acid phosphatase were found to have a rather flat distribution profile with about the same activities along the villi and in the crypts. The only exception was the ileum of suckling rat, in which especially the acid β-galactosidase showed higher activity in the villi and decreased toward the crypts. The results support the concept that the neutral β-galactosidase is responsible for the digestion of dietary lactose, while the acid β-galactosidase seems to have a different functional significance. That this enzyme is distributed in parallel with the acid phosphatase is consistent with the suggestion that the acid β-galactosidase may be a lysosomal enzyme.