Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 3, 2004
Publication Date: January 2, 2005
Citation: Taylor, J.B., Finley, J.W., Caton, J.S. 2005. Effect of the chemical form of supranutritional selenium on selenium load and selenoprotein activities in virgin, pregnant, and lactating rats. Journal of Animal Science. 83:422-429. Interpretive Summary: The effects of dietary selenium source and physiological state on selenium distribution and selenium-dependent enzyme activities in female rats were investigated. Simultaneously, lactating, pregnant and virgin rats of similar age were fed either a seleno-L-cystine (selenocystine) or seleno-L-methionine (selenomethionine) diet providing 2 mg selenium/g diet/day for 18 days. Heart, liver, uterus, muscle, spleen, lung, placenta, fetus and plasma selenium concentrations were greatest (P < 0.0002) in rats consuming selenomethionine. Lactating rats exhibited the highest (P < 0.005) selenium concentration in the heart, muscle, spleen, lung, and plasma, and when consuming selenomethionine, had the greatest (P = 0.02) selenium concentration in the brain. Pregnant rats had more (P < 0.0001) total selenium in the uterus than virgin and lactating rats. Pregnant and lactating rats were similar (P = 0.40) in body weight but heavier (P < 0.001) than virgin rats. Heart weight was heaviest (P < 0.003) in lactating and similar (P > 0.05) between pregnant and virgin rats. The liver was heaviest in lactating, intermediate in pregnant, and lightest in virgin rats (P < 0.0001). Uterus tissue weights were greatest (P < 0.004) for pregnant rats. For all weights obtained, virgin rats were consistently the least (P < 0.05). Thioredoxin reductase activity was greatest (P < 0.004) in the brain of pregnant rats, greatest (P < 0.004) in the liver of lactating rats, and greater (P < 0.03) /in the kidney of lactating and pregnant rats. Livers from pups nursing selenomethionine fed dams were heavier (P = 0.03) than those from the selenocystine fed group. These data clearly demonstrate that selenium from selenocystine is distributed differently than selenium from selenomethionine, and physiological changes associated with lactation influence tissue selenium concentration and thioredoxin reductase activity.
Technical Abstract: Selenium exists in many different forms. How and where selenium is used and ultimately eliminated from the body largely depends on the form consumed. Furthermore, the reproductive state of an animal can alter the rate selenium is utilized. To further explore how organically bound forms of selenium are metabolized and how this metabolism is altered due to reproductive state, we fed lactating, pregnant and virgin rats either a selenocystine or selenomethionine diet providing 2 ug selenium/g diet/day for 18 days. Regardless of physiological state, feeding selenomethionine resulted in more selenium being stored in most tissues than when selenocystine was fed. This effect is likely due to the direct incorporation of selenomethionine into protein in place of methionine. More selenium was found in tissues of lactating compared to pregnant and virgin rats. This result is probably due to the increased food intake that is commonly associated with lactation.