First report on the distribution of orally administered microcystin-LR in mouse tissue using an immunostaining method

The purpose of this study was to investigate the distribution of microcysti n-LR (MCLR) orally administered to mice using an immunostaining method. MCL R was orally dosed at 500 mu g/kg to aged Balb/C and ICR mice and their let hality was 23.9%. The former was more sensitive to MCLR than the latter, su ggesting that oral toxicity by MCLR is related to the animal strains tested , although the pathological and immunostaining changes were essentially the same in both strains. According to this method the distribution of MCLR an d related compounds were indicated as the red staining. Particularly, liver s of dead aged mice were intensively stained. The main route of absorption was considered to be the small intestine because the villi contained a larg e amount of MCLR in both surface epithelial cells and lamina propria, resul ting in erosion. The absorbed MCLR was contained in blood plasma and moved to the liver. lung, and heart, and finally to capillaries of the whole body . Excretion of MCLR was shown in the mucous from goblet cells in both the s mall intestine and large intestine. (C) 1999 Elsevier Science Ltd. All righ ts reserved.