Problems associated with the assay of arylsulphatases A and B of rat tissues

A method for the separation and purification of rat liver arylsulphatases A and B by gel filtration on Sephadex G-200 is described. The properties of the A enzyme and its molecular weight are similar to those of the corresponding ox liver enzyme. The B enzymes were found to be dissimilar. The method already developed for the assay of the corresponding enzymes from human tissues was shown to be unsuitable for the assay of the enzymes of rat tissues. A method of assay was developed which permits an approximate determination of the individual rat liver enzymes in a mixture of the two, but precise determination requires prior separation of the enzymes by gel-filtration chromatography.

Relative distribution of arylsulphatases A and B in rat liver parenchymal and other cells

The relative activities of arylsulphatases A and B were measured in rat liver parenchymal and non-parenchymal cells, in peritoneal macrophages and in a number of rat tissues. Although absolute values cannot be obtained, it was shown that the arylsulphatase B/arylsulphatase A activity ratio is much higher in non-parenchymal cells than in parenchymal cells. The ratios in adrenals, brain and testis are very similar to each other but differ from those found in spleen, kidney and liver. These ratio variations may be caused by alterations in the activity of the B enzyme rather than the A enzyme. The relatively high B enzyme/A enzyme ratios in all rat tissues explains why the method devised for the independent assay of human arylsulphatases A and B cannot be employed with rat tissues.

The heterogeneous distribution of acid hydrolases within a homogeneous population of cultured mammalian cells

1. Chinese-hamster ovary fibroblasts were cultured to provide a homogeneous cell population. Homogenates obtained from these cells were fractionated by centrifugation techniques and the resulting fractions were analysed for protein and for enzymes representative of certain subcellular particles. 2. Unlike those in rat liver homogenates, the mitochondrial and lysosomal populations proved impossible to separate by differential centrifugation owing to the similarity of their sedimentation properties. Their resolution was possible by using isopycnic centrifugation in a continuous sucrose density gradient. 3. The mitochondrial population equilibrated at a density of 1.17g.cm(-3) as in rat liver homogenates. However, the lysosomal population equilibrated at a lower rather than a higher density position than the mitochondria and the probable reasons for this are discussed. 4. The lysosomal population subdivided into two groups characterized by differences in acid hydrolase content and equilibrium densities. The fraction with a density of 1.15g.cm(-3) contained the majority of arylsulphatases A and B, of cathepsin and of beta-acetylglucosaminidase activities, whereas that with a density of 1.09g.cm(-3) contained the majority of the acid phosphatase and acid ribonuclease activities. The probable division of the lysosomal population of a single cell into a number of distinguishable subgroups is suggested.

Isolation and characterization of a rough microsomal fraction from rat kidney that is enriched in lysosomal enzymes

1. A special population of rough microsomal material (microsomes) rich in lysosomal acid hydrolases was separated by isopycnic centrifugation as a discrete fraction (RM(2)) from the bulk of rough microsomal material in rat kidney because of its greater density. 2. The specific activities of five acid hydrolases in the RM(2) fraction were approximately one-half those of a purified lysosomal (L) fraction and 10- to 30-fold greater than those of an ordinary rough microsomal (RM(1)) fraction. 3. These special rough microsomes have a distinctive ultrastructure and electron-cytochemical properties. Their cisternal content resembles the matrix of lysosomes in that it is electron-dense, osmiophilic and plumbophilic and gives a positive reaction for acid phosphatase activity. 4. Polyacrylamide-gel electrophoresis of soluble proteins from the L fraction resolved nine anionic glycoproteins, most of which exhibit acid hydrolase activities (Goldstone & Koenig, 1970, 1973; Goldstone et al., 1971a). The most anionic glycoprotein is the acidic lipoglycoprotein of the lysosomal matrix (Goldstone et al., 1970). 5. Polyacrylamide-gel electrophoresis of soluble proteins from the RM(2) fraction resolved two cationic glycoproteins with acid hydrolase activities (Goldstone & Koenig, 1973) and an anionic glycoprotein with the same electrophoretic mobility as the lysosomal lipoglycoprotein, but without its lipid constituents or capacity to bind the basic fluorochrome Acridine Orange. These constituents are considered to be the precursors of the lysosomal glycoproteins.

Biochemical changes in intestinal mucosa after experimental small bowel by-pass in the rat

1. After experimental small bowel by-pass the excluded segment of intestine, whether jejunum or ileum, shows a decrease (expressed in units/cm of intestine) in mucosal weight, protein, RNA and activity of all eight enzymes studied (leucyl β-naphthylamidase, alkaline phosphatase, β-galactosidase, α-glucosidase, aryl sulphatase, β-glucuronidase, cytochrome oxidase and catalase). There is a fall in DNA content and there are no consistent changes in enzyme activity when expressed as units/mg of DNA.

2. The intestine remaining in continuity after small bowel by-pass shows an increase (expressed in units/cm of intestine) in mucosal weight, protein, RNA and enzyme activity. There is an accompanying rise in DNA content in the intestine in continuity.

3. The increased values of all variables measured in the intestine in continuity are much more marked in ileum than in jejunum.

4. The adaptive changes seen in the by-passed intestine and the intestine in continuity are a result of ‘hypoplasia’ and ‘hyperplasia’ respectively.