Uptake of Labeled Alloxan in Mouse Organs and Mitochondriain Vivoandin Vitro*

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Abstract
[14C]2-Alloxan was administered in vivo and in vitro for study of the uptake of alloxan in different organs and their mitochondria of mice. After in vivo administration, radioactivity was demonstrated in all organs investigated, with quantitative differences: endocrine pancreas > liver > exocrine pancreas and heart. No significant difference was found between the i.v. and i.p. routes of injection. An in vivo uptake of alloxan was also found in mitochondria, with significant quantitative differences as to the origin of the organelles: endocrine pancreas > liver > exocrine pancreas and heart. Pretreatment with D-glucose caused significantly decreased uptake in liver, exocrine pancreas, and heart, but significantly increased uptake in endocrine pancreas; however, the uptake was significantly decreased in the mitochondria from all of these organs. In vitro uptake was observed in all kinds of mitochondria studied. This uptake was higher than the in vivo uptake in mitochondria from liver, exocrine pancreas, and heart, whereas the uptake in vivo was higher than the in vitro uptake in islet mitochondria. The presence of D-glucose did not affect the in vitro uptake of alloxan in mitochondria. In vivo, alloxan passes across plasma membranes and is taken up by mitochondria, and data obtained with mitochondrial subfractions may also indicate a passage across mitochondrial membranes. D-Glucose protection against alloxan diabetogenicity may be associated with prevention of mitochondrial uptake of alloxan. This prevention seems to be dependent on the metabolism of glucose.