Distribution and reuse of 76Se-selenosugar in selenium-deficient rats

Nutritional selenium compounds are transformed to the common intermediate selenide and then utilized for selenoprotein synthesis or excreted in urine mostly as 1 beta-methylseleno-N-acetyl-D-galactosamine (selenosugar). Since the biological significance of selenosugar formation is unknown, we investigated their role in the formation of selenoenzymes in selenium deficiency. Rats were depleted of endogenous natural abundance selenium with a single stable isotope (Se-82) and then made Se-deficient. Se-76-Sclenosugar was administered intravenously to the rats and their urine, serum, liver, kidneys and testes were subjected to speciation analysis with HPLC inductively coupled argon plasma mass spectrometry. Most Se-76 was recovered in its intact form (approximately 80% of dose) in urine within I h. Speciation analysis revealed that residual endogenous natural abundance selenium estimated by Se-77 and Se-78 was negligible and distinct distributions of the labeled Se-76 were detected in the body fluids and organs without interference from the endogenous natural abundance stable isotope. Namely, intact Se-76-selenosugar was distributed to organs after the injection, and Se-76 was used for selenoprotein synthesis. Oxidation to methylseleninic acid and/or hydrolysis of the selenoacetal group to methylselenol were proposed to the transformation of selenosugar for the reuse. Effective use of an enriched stable isotope as an absolute label in hosts depleted of natural abundance isotopes was discussed for application in tracer experiments. (c) 2006 Elsevier Inc. All rights reserved.