Effect of Vitamin E on Arginase Activity in the Liver and Kidneys of Testosterone-Treated and Castrated Rabbits

Eris i r M., N. Aydilek, M. Aksakal : Effect of Vitamin E on Arginase Activity in the Liver and Kidneys of Testosterone-Treated and Castrated Rabbits. Acta Vet. Brno 2005, 74:527-531. In the present study we examined the effect of vitamin E administration on arginase activity in the liver and kidneys of testosterone-treated and castrated rabbits. Forty-six 3-month-old male rabbits were divided into six groups: 1) control rabbits, 0.5 ml olive oil; 2) testosterone-treated rabbits, 10 mg of testosterone propionate dissolved in 0.5 ml olive oil; 3) bilaterally castrated rabbits, 0.5 ml olive oil; 4) vitamin E-treated rabbits, 100 mg/kg dl-α-tocopheryl acetate dissolved in 0.5 ml olive oil; 5) vitamin Eand testosterone-treated rabbits, 100 mg/kg dl-α-tocopheryl acetate and 10 mg testosterone propionate dissolved in 0.5 ml olive oil; 6) bilaterally castrated and vitamin E-treated rabbits, 100 mg/kg dl-α-tocopheryl acetate dissolved in 0.5 ml olive oil. The administration was done subcutaneously over 24 h for 40 days; then the arginase activities in the liver and kidneys were determined. Liver arginase activities in all the groups did not change significantly (p > 0.05). Kidney arginase activities were not affected by castration and vitamin E. Kidney arginase activity was found to have increased two-fold by testosterone treatment. Testosterone-induced arginase activity in the kidneys returned to normal level with a significant lowering effect of the combination of vitamin E and testosterone. These results indicate that vitamin E supplementation has a significant reducing effect on the testosterone-induced arginase activity in the kidneys. Vitamin E ameliorates the testosteroneinduced arginase activity in the kidneys. Arginase, testosterone, castration, vitamin E Arginase catalyzes the hydrolysis of L-arginine to form L-ornithine and urea (L-arginine amidinohydrolase, EC 3.5.3.1). This reaction comprises the final cytosolic step of the urea cycle, which provides the principal route for the disposal of nitrogenous waste from protein catabolism. Although arginase activity is most abundant in the mammalian liver where the urea cycle is most active, it is also found in non-hepatic tissues such as the kidney (Herzfeld and Raper 1976). The kidney does not contain an active urea cycle (Ratner and Petrack 1953), and kidney arginase is probably involved in the catabolism of arginine for use as a source of proline or glutamate, and polyamines (Kaysen and Strecker 1973; Manteuffel-Cymborowska et al. 1993; 1995). Since the liver and kidney arginase types differ in their regulation by certain steroid hormones (Kumar and Kalyankar 1984), by pattern of expression in patients with hyperargininemia (Spector et al. 1983), by electrophoretic mobility and by immunologic relatedness (Skryzpek-Osiecka and Porembska 1983; Porembska and Zamecka 1984; Porembska et al. 1993), they appear to be distinct polypeptides encoded by two different genes (Haggerty et al. 1983). Vitamin E maintains homeostasis in living cells (Gal lo-Torres 1980). Park and Tappel (1991) reported a relationship between vitamin E and arginase: rats fed a vitamin ACTA VET. BRNO 2005, 74: 527–531 Address for correspondence: Mine ERÍSÍR, Ph.D, Assoc. Professor of Biochemistry Department of Biochemistry College of Veterinary Medicine Firat (Euphrates) University, ELAZIG, 23119 TURKEY Phone: +90-424 237-0000, ext. 3960 Fax: +90-424 238-8173 E-mail: [email protected] http://www.vfu.cz/acta-vet/actavet.htm E supplemented diet had a lower liver arginase activity than those fed a vitamin E deficient diet. Arginase is known to be inducible by hormones (Mimic-Oka et al. 1971; Yamanaka et al. 1971; Kumar and Kalyankar 1984; Patnaik and Patnaik 1989). This effect can be prevented by vitamin E. Therefore, we examined the effects of vitamin E supplementation on arginase activity in the liver and kidneys of testosterone-treated and castrated rabbits. Materials and Methods Animals and Treatments The experiment was conducted on forty-six 3-month-old clinically healthy adult male New Zealand White rabbits weighing 2600 ± 300 g, which were housed one per cage at room temperature of 20 °C. During a 10-day adaptation period, the animals were given a basic diet and tap water ad libitum. At the end of this period, the rabbits were divided into six groups: 1) control rabbits, 0.5 ml olive oil; 2) testosterone-treated rabbits, 10 mg of testosterone propionate dissolved in 0.5 ml olive oil; 3) bilaterally castrated rabbits, 0.5 ml olive oil; 4) vitamin Etreated rabbits, 100 mg/kg dl-α-tocopheryl acetate dissolved in 0.5 ml olive oil; 5) vitamin Eand testosteronetreated rabbits, 100 mg/kg dl-α-tocopheryl acetate and 10 mg testosterone propionate dissolved in 0.5 ml olive oil; 6) bilaterally castrated and vitamin E-treated rabbits, 100 mg/kg d-α-tocopheryl acetate dissolved in 0.5 ml olive oil. This administration was done subcutaneously over 24 h for 40 days. At the end of the experiment, the rabbits were anesthetized and the liver and kidneys were excised and rinsed in cold saline (0.9 % NaCl). One gram of liver and kidney tissues was weighed and homogenized with 10 volumes of 10 mM Tris-HCl buffer pH (7.4) in a glass Potter Elvehjem homogenizer in an ice bath. The homogenates were centrifuged at 20 000 g for 10 min at 4 oC. The supernatants were used for the arginase assay. Arginase assay Arginase activity was measured by determining the increase in the amount of the reaction product, urea (Geyer and Dabich 1971). One unit (U) of enzyme activity was defined as μmole of the product formed per hour at 37 oC. The results are given as units/ mg of protein. Protein determinat ion The protein content of tissue samples was assayed according to the method of Lowry et al. (1951). The bovine serum albumin was used as the standard. Stat is t ical Analysis Results were expressed as mean ± SEM. Analysis of variance (ANOVA) followed by the Duncan test were used to determine significant differences among the groups. A 5% level of significance was used to establish differences.