Pergamon 0031-9384(94)00234-7 Physiology & Behavior, Vol. 57, No. 2, pp. 385-387, 1995 Copyright © 1995 Elsevier Science Ltd Printed in the USA. All rights reserved 0031-9384/95 $9.50 + .00 Lack of Sex and Estrous Cycle Effects on the Activity of Three Antioxidant Enzymes in Rats VANIA D'ALMEIDA,* DI~BORA CRISTINA HIPrLIDEI" AND MARIA EUGI~NIA DA SILVA-FERNANDES *l Departments of *Biochemistry and ?Psychobiology, Escola Paulista de Medicina, S6o Paulo, Brasil Received 14 March 1994 D'ALMEIDA, V., D. C. HIPOLIDE AND M. E. DA SILVA-FERNANDES. Lack of sex and estrous cycle effects on the activity of three antioxidant enzymes in rats. PHYSIOL BEHAV 57(2) 385-387, 1995.--The activity of antioxidant enzymes was inves- tigated in red blood cells of male and female Wistar rats 3-4 months of age. Superoxide dismutase (EC 1.15.1.1 ), catalase (EC 1.11.1.6), and glutathione peroxidase (EC 1. I 1.1.9) did not show any significant variation in the different phases of the estrous cycle. No differences were observed for the three enzymes related to the sex of young rats. The present data enable us to consider that sexual differences as well as the changes in estrous cycle do not interfere in erythrocyte antioxidant enzymatic defense of rats. Estrous cycle Sex differences Superoxide dismutase Catalase Glutathione peroxidase Free radicals REACTIVE oxygen species (ROS) have been related to many physiological and pathological processes. Organisms of an aer- obic environment have developed a defense mechanism with a group of essential enzymes: superoxide dismutase (SOD), cata- lase (CAT), and glutathione peroxidase (GPx). The balance among these enzymes and some nonenzymatic antioxidants (glu- tathione, vitamin E, ascorbic acid, and other elements) is impor- tant for the efficient removal of toxic oxygen from the intracel- lular space. Comparative studies of the activities of these enzymes have shown variations between species (4,8) and tissues (1), but the factors responsible for this variability are still unknown. Some authors suggest that there are differences related to sex (2,5,6), but the results are controversial. Another possibility is the influence of sexual hormones on the antioxidant defense (3,7,11,12). It is already known that vitamins A, C, and E are present in corpus luteum and that their concen- tration varies during the reproduction cycle (2). Evidences that SOD may be regulated by luteinizing hormone have been found (7,13). The analysis of SOD levels in thyroid of mice during the estrous cycle showed differences that result in a peak of enzyme activity in proestrus (13). These data led us to consider that fe- male rats could show alterations in the enzymatic antioxidant defense in the different estrous cycle stages. To clarify these points, we studied the activity of antioxidant enzymes (SOD, CAT, and GPx) in red blood cells (RBC) of male and female rats 3-4 months of age. In the case of female rats, we also determined the cycle stages for the evaluation of the relationship between estrous cycle and antioxidant enzymatic de- fense. METHOD Animals The animals, 15 male and 39 female Wistar rats, were ob- tained from the colony of the Department of Psychobiology of Escola Paulista de Medicina, S~o Paulo, Brazil. The animals (3- 4 months old) were kept in groups of two or three in wire cages with free access to food and water, and were maintained on a 12- h light/dark cycle with lights on at 0700 h. The females were divided in four groups according to their stage in the estrous cycle at the moment of blood removal. Determination of the Estrous Cycle Stages Rats were monitored for normal estrous cycling by daily vag- inal smears that were taken by a physiological saline lavage with an eyedropper. The solution was examined under a microscope for the cell content of the vaginal canal. Relative frequency of leukocytes, cornified, and nucleated epithelial cells were noted. Only female rats with a regular cycle served as subjects for this study. To assure that females were cycling normally, all subjects were initially monitored for 3 weeks to an adaptation period. Requests for reprints should be addressed to Maria Eug~nia da Silva-Fernandes, Ph.D., Department of Biochemistry, Escola Paulista de Medicina, Rua Botucatu, 862-Ed. Leal Prado -CP 20.372, Vila Clementino-04023-062, Sao Paulo, SP-Brasil. 385