Tissue Specific Expression of Glutathione S-transferases, Glutathione Content and Lipid Peroxidation in Camel Tissues

Abstract

Differential expression of glutathione S-transferase (GST) enzyme activity in various tissues of the camel was observed with a maximum activity in the liver. Compared with the rat and human livers, GST activity in camel liver was 50% lower than that of rat liver and similar to that of human liver. Extrahepatic tissues in camel have a comparable GST activity with those of similar tissues in the rat. Assay of GST activity using ethacrynic acid as substrate demonstrated maximum activity in the camel brain followed by intestine, liver and kidney. Microsomal GST activity in camel tissues was expressed in the order of liver > testis > intestine ≈ kidney ≈ brain. Phenotyping of GST was performed in camel hepatic and extrahepatic tissues using human specific antibodies to class α, μ, and π cytosolic GST isoenzymes and rat specific antibody to the microsomal GST. Western immunoblot and immunohistochemical analyses showed an abundant expression of GST α and μ in the camel liver, while π was very poorly expressed. Camel extrahepatic tissues however, had a significant expression of GST π. The camel GST isoenzymes were found to be predominantly expressed in the hepatocytes around the central vein with a gradual decrease in expression in the hepatocytes located toward the periphery. Kidney cortex exhibited a greater expression of the enzyme protein in the proximal tubules as compared to the glomeruli. Glutathione (GSH) concentration in rat tissues, except in the brain, was about 2-fold higher than that of camel tissues. Rate of NADPH-dependent microsomal lipid peroxidation was comparable both in the rat and camel tissues with the highest activity in the brain and lowest activity in the intestine. The differential expression of GST isoenzymes in different organs of the camel, GSH concentration and the rate of lipid peroxidation in different tissues may be important factors in determining the differential susceptibility of camel tissues to the toxic effects of xenobiotics.