The influence of alpha-tocopherol on arylsulfatases A and B in the liver of vitamin A-deficient rats

Liver lysosomal enzymes in rats during long-term dietary restriction. 1. Changes during the developmental period of life

The specific activities of the lysosomal enzymes acid phosphatase, beta-galactosidase, arylsulphatase B and cathepsin D were determined in homogenates of livers of rats fed ad libitum and of rats subjected to long-term dietary restriction (10%, 30% and 50% of diet consumed by the ad libitum group). Dietary restriction began soon after weaning and animals were sacrificed 3, 9, 15 and 24 weeks later. Dietary restriction influenced all four enzymes but the changes depended on the enzyme as well as on the degree and duration of the dietary restriction. Total activity of acid phosphatase increased significantly at 3 weeks of restriction but only in the 50% group. The activity returned to normal values at 9 weeks. Arylsulphatase B increased in all experimental groups with a more pronounced change observed at 3 weeks and in the more severely restricted rats. No notable change in the activities of beta-galactosidase and cathepsin D activities was observed. Changes in the liver ultrastructure paralleled the biochemical changes seen at 3 weeks. Numerous autophagic vacuoles and dense bodies resembling age pigments were formed in the hepatocytic cytoplasm. Mitochondrial enlargement, increased matrical density and rough endoplasmic reticulum fragmentation were also noted. Few of these changes were observed at 9 weeks, and the hepatocyte's morphology was virtually normal at 15 and 24 weeks. The marked changes seen at 3 weeks may be a manifestation of the body's adaptive processes to the nutritional stress.

Effects of alpha-tocopherol analogs on lysosome membranes and fatty acid monolayers

The surface pressures of alpha-tocopherol analogs, fatty acids, and their mixtures were measured in their spread monolayers at an air--water interface. The surface pressure--area isotherms for the mixed monolayers of alpha-tocopherol and either stearic acid, oleic acid or linoleic acid deviated positively from those calculated on the basis of the additivity rule, and the magnitude depended on the length of the phytyl side chain in alpha-tocopherol and on the degree of unsaturation of the fatty acid chains. Lysosome membranes of mouse liver were stabilized by addition of alpha-tocopherol. A decrease in the length of the phytyl side chain in alpha-tocopherol reduced its ability to stabilize lysosome membranes. A good correlation was obtained between the extent of stabilizing activity of alpha-tocopherol analogs on lysosome membranes and the degree of positive deviation of the surface pressure for their mixtures with fatty acids.

Vitamin A and lysosomal stability in rats fed an atherogenic diet

The relation between vitamin A status and lysosomal stability was studied in rats fed a high fat-cholesterol diet. Increase in the total activity of lysosomal enzymes as well as that in the nuclear fraction, intact lysosomal fraction and free activity (activity present in the 15,000 X g supernatant) in the liver was observed in rats fed an atherogenic diet with adequate vit. A. Vitamin A deficiency and hypervitaminosis (10,000 IU) augmented this increase in the total enzyme activity as well as the activity in the subcellular fractions except in the case of intact lysosomes where the activity was not significantly altered. At 2,000 IU, there was no significant alteration in either the total activity or the activity of the subcellular fractions. An analysis of the ratio of soluble activity (released from the lysosomes) to the activity present in the intact lysosomes, showed that hepatic lysosomal stability was decreased in the rats fed an atherogenic diet with normal dose of vit. A. Vitamin A deficiency as well as hypervitaminosis decreased the lysosomal stability still further. At a dose of 2,000 IU, lysosomal stability increased as compared to the rats fed an adequate dose of vit. A, while total lysosomal activity remained not significantly altered. Studies on the rate of release of enzymes from the lysosomes revealed that there was significantly more release of the enzyme between 30 and 45 min in the liver and aorta in the rats fed a high fat-cholesterol diet with adequate vit. A This release was still more in the rats fed a low dose of vit. A. At 2,000 IU, there was no significant difference in the enzyme release. But the pattern of change in the liver and aorta in the hypervitaminotic group was different. In the case of hepatic lysosomes, there was an increase in the enzymes released while in the aorta there was significant decrease. This has been attributed to the fact that lytic concentration of the vitamin A is not attained in the aorta.

Lysozyme activity in plasma and leucocytes in malnourished children

1. Lysozyme activity was estimated in plasma and leucocytes of twelve children suffering from kwashiorkor, thirteen children with ocular signs of vitamin A deficiency and ten apparently normal children acting as controls.

2. The results showed that the activity of lysozyme in leucocytes was significantly reduced in children with kwashiorkor and in vitamin A-deficient children. Following therapy, the levels of the enzyme in leucocytes were restored to normal.

3. The initial enzyme activity in the plasma of both groups of children did not differ significantly from the control value, and was not significantly changed after treatment.

4. It is suggested that the decreased activity of lysozyme is one of the factors responsible for diminished resistance to infection generally observed in malnourished children.

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.

On the postulated peroxidation of unsaturated lipids in the tissues of vitamin E-deficient rats

1. The micro-iodimetric method has been used to study some factors affecting the concentration of lipid peroxides in the adipose tissue of vitamin E-deficient rats.

2. Cod-liver oil methyl esters (CLOME) or maize oil methyl esters (MOME) with peroxide values ranging from 3 to 330 μ-equiv./g were given by mouth to vitamin E-deficient rats deprived of food before and after the dose. Lipid peroxides did not accumulate in the adipose tissue of these rats.

3. Experiments with dietary CLOME and MOME of varying peroxide values (2–230 μ-equiv./g) showed that exogenous lipid peroxide accumulates in the adipose tissue when the rats received these lipids at 10% in the diet for 4 weeks, but not if the dietary concentration was only 4% or if the diet with 10% lipid was given for 5 days only.

4. Rats were given dietary CLOME for 4 weeks. Their adipose tissue was then found to contain about 50 μ-equiv. lipid peroxide/g. They were divided into three groups. One group was given a fat-free diet and, after 10 days, the adipose tissue concentration of lipid peroxide had decreased to about 10 μ-equiv./g. The other groups were given the fat-free basal diet supplemented with vitamin E or DPPD (N,N′-diphenyl-p-phenylenediamine). Neither supplement significantly affected the rate of disappearance of the peroxides from the adipose tissue.

5. It was shown that neither α-tocopherol nor DPPD reacted with the lipid peroxides of CLOME or MOME in vitro, at room temperature or even after 65 h at 37°.

6. It was concluded that unsaturated lipids do not become peroxidized after incorporation into the adipose tissue of vitamin E-deficient rats. Lipid peroxides taken up from the diet into the adipose tissue are not of fleeting existence, having a half-life of about 6 days. Dietary vitamin E probably prevents the accumulation of exogenous lipid peroxides in the adipose tissue by reinforcing the barrier to their absorption in the gut.

7. These studies provide further evidence that current concepts of lipid peroxidation in vitamin E-deficient animals are incorrect. In fact, vitamin E-deficient animals have low concentrations of peroxide in their adipose tissue, unless they have received large amounts of unsaturated lipid for long periods, and the role of vitamin E in controlling this concentration is not due to any effect on peroxidation in vivo.

Vitamin E and stress. 7. The interrelationships between polyunsaturated fatty acid stress, vitamin A and vitamin E in the rat and the chick

1. The nature of the relationship between vitamins A and E has been studied in the rat and the chick.

2. Stress induced by diets rich in polyunsaturated fatty acids (PUFA) was found to have no effect on the liver vitamin A reserves of vitamin E-deficient rats given dietary vitamin A or repeated small oral doses of vitamin A.

3. Dietary PUFA did not affect the liver vitamin A reserves of young rats given necrogenic diets deficient in vitamin E and selenium, nor were these reserves affected by the onset of liver necrosis or its prevention by Se.

4. The effect of dietary PUFA on the rate of depletion of liver vitamin A reserves in weanling rats or rats depleted initially of vitamins A and E and then given a single large dose of vitamin A was studied over periods from 2 to 12½ weeks. In three experiments the dietary PUFA did not significantly accelerate vitamin A depletion. In one experiment the depletion rate was increased, but this was not reversed by dietary vitamin E and thus could not be attributed to an enhancement of peroxidation in vivo but rather to a toxic effect. The effect of vitamin E in these experiments was not consistent but, in general, it slightly decreased the rate of depletion.

5. Large doses of vitamin A did not affect the metabolism of small amounts of [14C]D-α-tocopherol in the vitamin E-deficient rat or chick, when interaction of the two vitamins in the gastro-intestinal tract was avoided.

6. Large doses of vitamin A (40000 i.u. in total) given to vitamin E-deficient chicks receiving a diet containing 1% linoleic acid (as maize oil esters) did not accelerate the onset of encephalomalacia and therefore failed to exert a pro-oxidative effect on tissue tocopherol.

7. The conclusion drawn from these experiments was that any relationship that may exist in vivo between vitamins A and E is not concerned with an effect of vitamin E in preventing oxidation of vitamin A. A critical review of the literature on the nature of the relationship in general supports this view.

Role of vitamin A in sulphate metabolism. Studies on the enzymic activation of sulphate by various tissue extracts of normal and vitamin A-deficient rats

1. The enzymic activation of sulphate by various tissue extracts of vitamin A-deficient rats and their pair-fed controls was studied. 2. Vitamin A deficiency does not impair the enzymic activity in liver, colon and brain. However, a significant decrease in activity was observed in epiphyseal cartilage.