Abstract
The objective of the present study was to evaluate the effects of microcystin-LR (MCLR) on the activity of membrane enzymes from intestinal mucosa. In addition, serum chemistry and peroxidative status of both serum and intestinal homogenate were evaluated after treatment with MCLR. Wistar rats were treated with intraperitoneal injection of either 100 μg pure MCLR/Kg body weight or saline solution. A significant increase in liver weight and altered serum enzyme activities were found in MCLR-treated rats, indicating damage to the liver in these rats, as previously suggested. A higher specific activity of sucrase (1.5-fold) was observed after the administration of MCLR, whereas other intestinal apical membrane enzymes, such as lactase, maltase and alkaline phosphatase were not modified by the treatment. The specific activities of acid phosphatase and succinate dehydrogenase, markers for lysosomal and mitochondrial membranes, respectively, were also increased (32% and 60%, respectively) in treated rats. The analysis of lipid peroxidation showed that the peroxidative status was increased in both serum and intestinal mucosa from MCLR-treated rats, reflecting an excess production of oxygen free radicals induced by this cyanobacterial toxin. In conclusion, this study shows that acute exposure to MCLR affects the intestinal physiology by modifying the intestinal peroxidation status as well as the activity of membrane enzymes.
Resumen
En este trabajo se analiza la acción de la toxina microcistina-LR (MCLR) sobre la actividad de diversas enzimas de membrana en la mucosa intestinal. Para ello, se utilizan ratas Wistar a las que se inyecta por vía intraperitoneal 100 μg MCLR/Kg peso corporal o bien solución salina (grupo control). Asimismo, se realiza un estudio bioquímico en suero, y se determina el grado de peroxidación lipídica en la mucosa intestinal y suero de estos animales tras el tratamiento con MCLR. La toxina induce daño hepático severo en las ratas tratadas, como lo demuestra el aumento del peso del hígado y diversas alteraciones de las enzimas hepáticas en suero. Por lo que respecta a las enzimas de membrana, las ratas tratadas con MCLR presentan un aumento en la actividad de la enzima sacarasa en la mucosa intestinal, no alterándose otras enzimas apicales como la lactasa, maltasa o fosatasa alcalina. MCLR también produce un aumento en la actividad de la fosfatasa ácida y succinato deshidrogenasa, marcadores respectivos de membranas lisosomales y mitocondriales. Además, los niveles de peroxidación lipídica en suero y mucosa intestinal aparecen anormalmente elevados tras el tratamiento, como consecuencia de la producción excesiva de radicales libres de oxígeno inducida por la toxina. Por consiguiente, la intoxicación aguda con MCLR afecta a la fisiología intestinal provocando una modificación del estado peroxidativo y alterando la actividad de las enzimas de membrana intestinales.
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Moreno, I.M., Mate, A., Repetto, G. et al. Influence of Microcystin-LR on the activity of membrane enzymes in rat intestinal mucosa. J. Physiol. Biochem. 59, 293–299 (2003). https://doi.org/10.1007/BF03179887
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DOI: https://doi.org/10.1007/BF03179887