Some aspects of nitrogen metabolism in Biomphalaria alexandrina snails treated with selenium.

The toxicity of selenium on Biomphalaria alexandrina snails, intermediate host for Schistosoma mansoni, was traced by studying its effect on the protein profile, free amino acids (FAA) and some urea cycle enzymes, namely, ornithine aminotransferase, argininosuccinate synthetase and arginase in hepatopancreas of snails. The results revealed that treatment with 15 ppm selenium dioxide (SeO2) caused an elevation in the protein content and a variation in the percentage and number of the different polypeptides as obtained by gel electrophoresis, and a remarkable reduction in all FAA except arginine alanine and threonine. On the other hand, the activity of ornithine, aminotransferase was elevated whereas that of arginase was reduced. The study is a trial to focus some metabolic disorders caused by SeO2 on the physiological status of these intermediate host snails, which may greatly control parasite-host association and thus the life-cycle of the parasite within its respective host may be somewhat disturbed.