Plasma selenium and glutathione peroxidase activity fluctuate during the rat estrous cycle

Abstract

The effect of the estrous cycle on selenium status was studied in chronically-catheterized Sprague-Dawley rats. Plasma and red blood cell selenium concentrations and glutathione peroxidase (GPx) activities were measured in five chronically-catheterized rats throughout two consecutive 4-d estrus cycles. Fifteen blood samples were serially drawn from each animal during each 4-d cycle. Plasma selenium and GPx activity and RBC selenium concentrations fluctuated significantly throughout the estrus cycle. Plasma selenium concentration reached a peak during proestrus and was significantly greater (P<0.05) than that observed during the other days of the estrous cycle. Plasma GPx activity peaked during early proestrus and late metestrus. RBC selenium peaked during estrus. These results suggest that hormonal fluctuations and the stage of the reproductive cycle should be considered when assessing female selenium status and when establishing dietary selenium recommendations.