TISSUE-SPECIFIC EXPRESSION OF GLUTATHIONE S-TRANSFERASES, GLUTATHIONECONTENT AND LIPID-PEROXIDATION IN CAMEL TISSUES

Differential expression of glutathione S-transferase (GST) enzyme acti vity in various tissues of the camel was observed with a maximum activ ity in the liver. Compared with the rat and human livers, GST activity in camel liver was 50% lower than that oi rat liver and similar to th at of human liver. Extrahepatic tissues in camel have a comparable GST activity with those of similar tissues in the rat. Assay of GST activ ity using ethacrynic acid as substrate demonstrated maximum activity i n the camel brain followed by intestine, liver and kidney. Microsomal GST activity in camel tissues was expressed in the order of liver > te stis > intestine approximate to kidney approximate to brain. Phenotypi ng of GST was performed in camel hepatic and extrahepatic tissues usin g human specific antibodies to class alpha, mu, and pi cytosolic GST i soenzymes and rat specific antibody to the microsomal GST. Western imm unoblot and immunohistochemical analyses showed an abundant expression of GST cc and mu in the camel liver, while pi was very poorly express ed. Camel extrahepatic tissues however, had a significant expression o f GST pi. The camel GST isoenzymes were found to be predominantly expr essed in the hepatocytes around the central vein with a gradual decrea se in expression in the hepatocytes located toward the periphery. Kidn ey cortex exhibited a greater expression of the enzyme protein in the proximal tubules as compared to the glomeruli. Glutathione (GSH) conce ntration in rat tissues, except in the brain, was about 2-fold higher than that of camel tissues. Rate of NADPH-dependent microsomal lipid p eroxidation was comparable both in the rat and camel tissues with the highest activity in the brain and lowest activity in the intestine. Th e differential expression of GST isoenzymes in different organs of the camel, GSH concentration and the rate of lipid peroxidation in differ ent tissues may be important factors in determining the differential s usceptibility of camel tissues to the toxic effects of xenobiotics. (C ) 1997 Elsevier Science Inc.