Elena Valdés

Modulation of rat liver peroxisomal and microsomal fatty acid oxidation by starvation

In this work the microsomal lauric acid ω‐hydroxylation, fatty acid peroxisomal β‐oxidation, and the levels of cytochrome P‐450 IVAI were studied in liver tissue from starved rats. Starvation increased the peroxisomal β‐oxidation and the microsomal hydroxylation of fatty acids. The correlation between these activities would support the proposal that both processes are linked, contributing in part to catabolism of fatty acids in liver of starved rats.

Effects of Chronic Ethanol Consumption on Extramitochondrial Fatty Acid Oxidation and Ethanol Metabolism by Rat Kidney

1. We evaluated the effects of chronic ethanol consumption on microsomal and peroxisomal fatty acid oxidation and on ethanol oxidation by the kidney. 2. When mature rats were fed 20% ethanol for 10 weeks, an increase in alcohol dehydrogenase and catalase activities were observed in the kidney. 3. Renal microsomal and peroxisomal oxidation of fatty acids also increased by the treatment, but total cytochrome P450 content did not. 4. We concluded that chronic ethanol consumption results in an increased extramitochondrial disposition of fatty acids and ethanol oxidation by the kidney.

DDT-dehydrochlorinase—I. Purification and characterization

1. 1. DDT-dehydrochlorinase (E.C. 4.5.1.1) from Musca domestica L. has been purified extensively by ammonium sulfate precipitation, hydroxylapatite adsorption and elution, ethanol precipitation, and Sephadex and DEAE-Sephadex column chromatography. 2. 2. The native enzyme appears to have a molecular weight of 120,000 and it is formed by four monomers of a molecular weight of 30,000 each. 3. 3. Aggregates of monomers to give a molecular weight of 60,000 are inactive. Activity appears only with aggregates of a minimum molecular weight of 90,000. 4. 4. Aggregation of monomers is induced by DDT but not by glutathione, which is required for enzyme activity. However, glutathione prevents dissociation of the enzyme into monomers and polypeptides of lower molecular weights. 5. 5. The mechanism whereby DDT produces aggregation of monomers and glutathione prevents the dissociation of aggregates remains to be established.

Nutritionally triggered alterations in the regiospecificity of arachidonic acid oxygenation by rat liver microsomal cytochrome P450.

Cytochrome P450-dependent oxidation of arachidonic acid was studied in liver microsomes from normal fed, protein-energy malnourished, and refed rats. The overall rate of arachidonic acid oxidation was very similar in microsomes from the three groups, but microsomes from malnourished rats showed a higher turnover rate than microsomes from normal fed and refed rats. The regiospecificity of cytochrome P450 oxidation of arachidonic acid was drastically altered by the animal nutritional status. Thus, protein-energy malnutrition results in a clear stimulation of total omega and omega-1 hydroxylation, concomitant with a marked decrease in olefin epoxidation and allyllic oxidations. These changes, as well as the documented biological activity of some of the cytochrome P450 arachidonate metabolites, suggest that protein-energy deficiency might help to select P450 isozymes which are probably involved in key monooxygenation reactions of physiological substrates.

Peroxisomal and Microsomal Fatty Acid Oxidation in Liver of Rats after Chronic Ethanol Consumption

1. Microsomal P450 and peroxisomal fatty acid oxidation activities were studied in liver of rats after long-term ethanol consumption. 2. Ethanol increased the microsomal lauric acid omega-hydroxylation and the aminopyrine N-demethylation catalyzed by cytochrome P450. 3. Ethanol increased peroxisomal beta-oxidation of palmitoyl CoA and catalase activity in liver. 4. Both microsomal and peroxisomal activities behaved in a coordinate way in the liver of rats with long-term ethanol consumption. 5. These results would support a role of microsomal omega-hydroxylation and peroxisomal beta-oxidation of fatty acids in an extramitochondrial pathway of lipid oxidation in the liver.

Starvation effect on rat kidney peroxisomal and microsomal fatty acid oxidation: A comparative study between liver and kidney

Microsomal lauric acid 12‐hydroxy lauric acid (ω)‐hydroxylation and fatty acid peroxisomal β‐oxidation were studied in kidney tissue from starved rats. Starvation increased the microsomal ω‐hydroxylation and peroxisomal β‐oxidation of fatty acids with a high correlation between both processes. Earlier, we reported similar results in liver. Our results support the hypothesis that the role of microsomal fatty acids ω‐hydroxylation is the generation of substrate for peroxisomal β‐oxidation, with the final purpose of contributing to a catabolic or gluconeogenic pathway from fatty acids.

Microsomal and peroxisomal fatty acid oxidation in bile duct ligated rats: a comparative study between liver and kidney.

1. Microsomal cytochrome P-450 and peroxisomal fatty acid oxidation was studied in the kidney of rats 7 days after bile duct ligation (BDL) and a comparative study between kidney and liver was done. 2. Only in the liver did cholestasis decrease the cytocrome P-450 content and the peroxisomal fatty acid beta-oxidation, the catalase activity, and the microsomal metabolism of lauric acid and aminopyrine. 3. In contrast, cholestasis did not influence these activities in the kidney. The microsomal and peroxisomal activities studied responded in a coordinate way to cholestasis. 4. These results could suggest the possibility of a cause-and-effect relationship between microsomal cytochrome P-450 and peroxisomal activity.

Androstenedione metabolism in streptozotocin diabetes and fasting male rats: Similarities and differences

Abstract The oxidation products of androstenedione catalysed by liver microsomes from streptozotocin-diabetic and fasting male rats have been studied. Diabetic and starved rats displayed increased activity for 7α androstenedione hydroxylase and diminished activity for 16a androstenedione hydroxylase in comparison to the normal animals. Insulin treatment to diabetic rats did not antagonize the changes observed in untreated diabetic rats. Opposite to the diabetic state, the rate of 6β-OHA and 2β-OHA formation were increased in the course of the starved periods. The results suggest that under diabetes and fasting conditions distinct alterations occur in specific individual cytochrome P-450s.

A Novel Reverse Phase HPLC Method to Separate and Quantify Androstenedione and Its Stereospecific Hydroxyaromatic Derivatives

Abstract Reverse - phase High Pressure Liquid Chromatography with a gradient elution on a LiChrocart 250-4 LiChrospher 100 RP-18 column has been used to separate and quantify 7 α-hydroxyandrostenedione (7α-OHA), 6β-hydroxyandrostenedione (6β- OHA), 16α-hydroxyandrostenedione (16α - OHA), 2 β - hydroxyandrostenedione (2 β - OHA), testosterone (T) and androstenedione (A). These steroids are the major products of androstenedione hydroxylation by adult rat liver microsomes. Separation was achieved in 30 minutes by using a linear gradient of acetonitrile (CH3CN) and water in increasing amounts from 30% to 60% of the first solvent (CH3CN). This new method compares very favourable with other methods already reported for studying microsomal hydroxylations of androstenedione in different positions of the steroidal skeleton.

Microsomal and Peroxisomal Fatty Acid Oxidation in Liver of Rats With Bile Duct Ligation and Two-Thirds Hepatectomy

Microsomal cytochrome P450 and peroxisomal activity were studied in liver of rats 7 days after two-thirds hepatectomy or bile duct ligation (BDL). Both surgical models decreased the hepatic microsomal cytochrome P450 content, but only cholestasis, produced by BDL, decrease the microsomal metabolism of lauric acid and aminopyrine, peroxisomal fatty acid beta-oxidation and catalase activity. The microsomal and peroxisomal activities responded in a coordinate way to cholestasis and two-thirds hepatectomy. These results suggest a cause-effect relationship between the microsomal cytochrome P450 and peroxisomal activity.