OTC has been detected at nanogram to low-microgram per liter levels in wastewater effluents and natural waters. OTC can bioaccumulate in various organisms including invertebrates and fish in food chain and enter human bodies by water drinking and food intake such as milk, meat and eggs, posing a threat to human health. OTC can also be taken up by blood cells. The Joint FAO/WHO Expert Committee of Food Additives and Contaminants, at its 50th Meeting in 1998, established a group acceptable daily intake of 0,0.03 mg kg21 body weight for the tetracyclines, tetracycline and chlortetracycline ), alone or in combination. The committee also recommended maximum residue limits of 100 mg L21 in milk and muscle of all food-producing species,. The toxicity of OTC residues in the environment including animal food, soils, surface and ground water, has attracted widespread attention,,,. OTC can inhibit the antibody levels in fish, induces DNA damage in carp SR 142948 kidney cells, has teratogenic effects on carp embryos, interacts with cytoplasmic protein synthesis, and induce blood disorder in Juvenile Nile Tilapia Oreochromis niloticus. OTC also has effect on the secretion kinetics of the rat exocrine pancreas and can lead to the decrease in trypsin level in male wistar rats,. Red blood cells, also referred to as erythrocytes, are the most abundant cells in the bloodstream. The M62812 primary function of RBCs is to transport oxygen from the lungs to various parts of the body. In addition, RBCs are also a key player in getting waste carbon dioxide from the tissues to the lungs of the body where it is expelled, and regulate blood pH. However, intake of hazardous substances may result in injury of RBCs, affecting its functions. Test principle: GSH is an important nonenzymatic antioxidant. It participates in the maintaining of redox equilibrium which may alleviate cellular oxidative injury. In this work, NDA was used to label the intracellular GSH of hRBCs. Nonfluorescent NDA can readily penetrate the cell membrane, interacting with the nonfluorescent GSH to produce a green fluorescent GSH-NDA derivative. The fluorescence intensity of GSH-NDA derivative was directly proportional to the intracellular content of GSH by fluorescence image analysis. NDA can react concomitantly with the amino and thiol groups of GSH, and no additional nucleophile reagent is required. So the bifunctional reaction is rapid, nonenzymatic, and highly selective.