Enzyme activities in liver and brain fractions from alcoholic and control rats

Effects of several alcohols on glycosidase activities in rat liver and brain

1. beta-D-Galactosidase, beta-D-glucuronidase and beta-NAc-D-glucosaminidase spec. acts from liver displayed statistically significant differences after treatments with certain alcohols. 2. No statistically significant difference was found for the kinetic parameters (Km and Vmax) of the indicated glycosidase activities. 3. beta-D-Glucuronidase and beta-NAc-D-glucosaminidase spec. acts from brain tissue showed statistically significant differences after treatments with certain alcohols. 4. beta-D-Glucuronidase and beta-NAc-D-glucosaminidase activities from liver showed a statistically significant decrease in the presence of in vitro ethanol. Tolerance effects were not observed.

Effects of glycosylation enzymes from membrane fractions, induced by chronic ethanol administration

To study the effect of chronic ethanol administration on the enzyme activities involved in the glycosylation processes (glycosidases and glycosyltransferases), we used 6-week ethanol-treated female Wistar rats and pair-control rats. Biological material was membrane fractions of microsomes and plasma membrane obtained by subcellular fractionation technique. Ethanol treatment increased with statistical significance the Vmax of N-acetyl-beta-D-glucosaminidase (P less than 0.10), beta-D-glucuronidase and alpha-D-mannosidase (P less than 0.001) activities from microsomal fractions and likewise it increased the Km value of beta-D-glucuronidase (P less than 0.001). In vitro doses of ethanol (0.1-1.7 M) were added to delucidate hypothetical membrane tolerance responses. However in vitro addition of ethanol provoked no differential effects in treated and untreated rats. Glycosyltransferase assays were carried out using [14C]sugar derivatives. We detected several glycosyltransferase activities in both microsome and plasma membrane fractions. Chronic ethanol exposure appeared to affect N-acetyl-neuraminyltransferase activity from both membrane fractions, producing a greatly increased incorporation in the presence of asialofetuin. Glucosyl and mannosyltransferase activities from plasma membrane fractions were also altered by ethanol treatment, producing an increased enzyme activity when reaction was performed in the presence of phosphatidylcholine + dolichol-phosphate liposomes.

Purification and properties of beta-N-acetylhexosaminidase A from pig brain

1. Adult pig brain beta-N-acetylhexosaminidase was separated into four different forms by ion exchange chromatography on diethylaminoethyl-cellulose. 2. Form A was purified 1300-1500 fold by an unusual procedure, the technique of ampholyte displacement, followed by chromatography on concanavalin A Sepharose. 3. The enzyme catalyses the hydrolysis of both beta-N-acetylglucosaminides and beta-N-acetylgalactosaminides. 4. The kinetic studies support the evidence of the association of both activities to a single protein, and at the same active site. 5. A natural substrate, N,N'-diacetylchitobiose, is also hydrolyzed, but not ovalbumin. 6. This enzyme may be considered as an exoglycosidase.

Chronic alcohol consumption induces lipofuscin deposition in the rat hippocampus

Previous investigations have suggested that chronic alcohol consumption accelerates a number of age-related changes in the cerebellar cortex and hippocampal formation. In the cerebellum, alcohol-feeding has been shown to accelerate the intracellular deposition of lipofuscin. In order to determine whether alcohol administration has a similar effect on hippocampal lipofuscin deposition, we studied the pattern of lipofuscin deposition in alcohol-fed rats for periods of 1, 3, 6, 12 and 18 months and compared the results with those obtained in the respective pair-fed controls. A precocious and progressive deposition of lipofuscin pigment was found in both CA1 and CA3 neurons in Ammon's horn hippocampal fields after 3 and 6 months of alcohol feeding, respectively. These results parallel those observed during normal aging and reinforce the hypothesis of a close link between chronic alcohol consumption and a premature nerve cell aging.

Alterations in the activities of subcellular fractions marker enzymes in rat liver and brain by hydrocortisone and corticosterone treatment

The effect of subcutaneous injection of hydrocortisone and corticosterone on the activity values of some subcellular fractions marker enzymes from rat liver and brain was investigated and compared with controls (without treatment with hormones). The following enzymes were studied (subcellular fraction are shown between parentheses): N-acetyl-beta-D-glucosaminidase and beta-glucuronidase (lysosomes); succinate dehydrogenase = SDH (mitochondria); glucose-6-phosphatase (endoplasmic reticulum); 5'-nucleotidase and Na+-K+-Mg2+ ATPase (plasma membrane). The specific activity of lysosomal enzymes from liver showed no change when rats were injected either with hydrocortisone or corticosterone. The same enzymes from brain showed significant increases in their activities with both hydrocortisone or corticosterone except beta-glucuronidase; this enzyme gave activity values remaining between the control levels, after treatment with corticosterone. The activity of mitochondrial SDH was increased after corticosterone injection either in liver or brain. After hydrocortisone injection, its activity rises significantly in brain (72%), but it falls in liver compared to the control values. Glucose-6-phosphatase behaves similarly in brain or liver fractions; its activity increases always after corticosterone treatment and decreases by hydrocortisone. The plasma membrane marker enzymes did not change practically in brain fractions, excepted Na+-K+-Mg2+ ATPase which tends to rise its activity after hydrocortisone injection. In liver fractions, both 5'-nucleotidase and Na+-K+-Mg2+ ATPase activities increase either by corticosterone or hydrocortisone treatment, except 5'-nucleotidase which specific activity decreases in liver after hydrocortisone treatment.

Effects of oestradiol, testosterone and medroxyprogesterone on subcellular fraction marker enzyme activities from rat liver and brain

The following enzymes have been studied (subcellular fractions are shown between parentheses): NAG and beta-glucuronidase (lysosomes); SDH (mitochondrial); glucose-6-phosphatase (endoplasmic reticulum); 5'-nucleotidase and (Na+, K+)Mg2+ ATPase (plasma membranes). Alterations on their activities were observed after subcutaneous injection of sex hormones, compared with controls. NAG activity from liver was always significantly decreased in lysosomal and microsomal fractions after the hormonal treatment. In the same conditions, NAG from brain was always increased. beta-Glucuronidase behaves like NAG in brain; in liver it was not modified by testosterone and it was slightly increased in lysosomal fraction after oestradiol treatment. SDH activity was not modified in mitochondrial fractions from liver, but this activity was always significantly increased in brain. Glucose-6-phosphatase activity was always significantly decreased in microsomal fractions from liver. It was increased in brain after oestradiol and testosterone injection, but medroxyprogesterone treatment caused a decreased activity. 5'-Nucleotidase and (Na+, K+)Mg2+ ATPase from brain were significantly increased in microsomal fractions by oestradiol and testosterone. Medroxyprogesterone, however, caused an increase in ATPase, but did not affect 5'-nucleotidase. Both activities in liver were decreased by oestradiol and increased by testosterone, but medroxyprogesterone caused (Na+, K+)Mg2+ ATPase to rise and 5'-nucleotidase to fall.

Lipofuscin granules in cerebellar interneurons after long-term alcohol consumption in the adult rat

Lipofuscin deposition in nerve cells is one of the most reliable and consistent neurocytological features correlated with ageing. Purkinje cells of long-term alcohol-fed rats show large agglomerates of lipofuscin granules after six months of alcohol experiment, whereas in normal biological ageing, this happens only after 25 months of age. Cerebellar interneurons have specific patterns of lipofuscin accumulation during ageing concerning both its morphological type and chronology of deposition. We studied the effects of chronic alcohol treatment on cerebellar interneurons taking particular account of lipofuscin pigment accumulation. Control and alcohol-fed groups for 1, 3, 6, 12 and 18 months were used. A precocious and progressive accumulation of lipofuscin granules occurred in granule, Golgi and basket cells. Stellate cells remained pigment-free. The lipofuscin deposited in the granule and Golgi cells was of the granular type, whereas that of basket and stellate cells was lamellar (fingerprint-like pattern). These results parallel those observed during normal ageing, and reinforce the hypothesis of the existence of a close relationship between chronic alcohol consumption and precocious nerve cell ageing.

Hepatic thyroid hormone levels following chronic alcohol consumption: direct experimental evidence in rats against the existence of a hyperthyroid hepatic state

To study the effect of chronic alcohol consumption on hepatic levels of thyroid hormones, female Sprague-Dawley rats (n = 24) were pair-fed nutritionally adequate liquid diets containing either ethanol (36% of total calories) or isocaloric carbohydrates for 21 days. Compared to controls, chronic alcohol consumption failed to result in a significant change of hepatic thyroid hormone levels (thyroxine: 14.7 +/- 1.81 ng per gm of liver wet weight vs. 15.0 +/- 1.59; triiodothyronine: 2.60 +/- 0.16 ng per gm of liver wet weight vs. 2.66 +/- 0.18). Similar results were obtained when the hepatic levels of thyroid hormones were expressed per total liver, per gram of liver protein or per 100 gm of body weight. Moreover, prolonged alcohol ingestion led to a significant reduction of serum total thyroxine by 31.6% (p less than 0.001), free thyroxine by 38.9% (p less than 0.02), total triiodothyronine by 40.2% (p less than 0.001) and free triiodothyronine by 56.1% (p less than 0.001) when compared to their pair-fed controls, whereas thyroid-stimulating hormone levels remained virtually unchanged. These data, therefore, clearly show that chronic alcohol consumption is incapable of creating a hyperthyroid hepatic state in rats, and limit the rationale for antithyroid treatment in patients with alcoholic liver disease.

Lipofuscin granules in Purkinje cells after long-term alcohol consumption in rats

The increased number of lipofuscin granules in Purkinje cells from chronic alcohol-fed rats was studied by morphometric methods. These granules were autofluorescent and had marked acid phosphatase activity. No significant changes were found in the mean nuclear and perikaryon volumes when alcohol-fed and control groups were compared. The number of lipofuscin granules per unit of surface area of cell cytoplasm (Na) and their volumetric density (Vv) were significantly greater in alcohol-fed groups than in controls. These values were also significantly different when the 6- and 12-month control groups were compared. Na and Vv values in alcohol-fed groups increased progressively. The increased number is probably related to disturbances in neuronal cell metabolism. The importance of age and malnutrition in the formation of these granules was also considered.