METABOLIC RELEVANCE OF SELENIUM IN THE INSECT CORCYRA-CEPHALONICA - UPTAKE OF SE-75 AND SUBCELLULAR-DISTRIBUTION

Requirement, uptake, and subcellular distribution of (Na2SeO3)-Se-75 i n the larvae of the insect C. cephalonica was investigated. That Se is well tolerated by C. cephalonica upto an added level of 2 ppm in the diet is suggested by the observed increase in body weight, total prote in, and succinate dehydrogenase levels. Significant increases in the S tate 3 respiration ensued with Se supplementation up to 2 ppm in the m itochondrial oxidation of D-glycerol 1-phosphate, succinate and NADH, along with concomitant unaltered State 4 respiration, leading to enhan ced RCR values. Maximal uptake of Se-75 was registered in the larvae m aintained on basal diet when subjected to short-term exposure to 0.5 p pm Se-75 level. When exposure level was further increased up to 20 ppm , the observed decrease in the uptake of Se-75 suggested that Se statu s of larvae itself controlled the tissue uptake. Subcellular distribut ion pattern revealed maximal incorporation of Se-75 (cpm/g tissue) in the supernatant fraction, whereas, maximal specific Se-75 activity (cp m/mg protein) was associated with the mitochondrial fraction. Autoradi ography of the soluble fractions indicated the presence of single sele noprotein in the larval group with short term 2 ppm Se-75 exposure. In herent Se controls both the extent and the nature of distribution of m itochondrial Se-75 incorporation. Uptake of Ca-45 by the insect mitoch ondria was enhanced by dietary Se up to 2 ppm but was unaffected by ad dition of in vitro Se-75 in the medium. A more fundamental role for Se in the mitochondrial energy metabolism emerges from these studies.