Kidneys are pair organs located in the abdominal cavity and they filter blood, excrete harmful substances and in general maintain the homeostasis of the body’s internal environment. Because of their anatomy and function, they are susceptible to damage caused by toxic substances such as environmental chemicals, metals and various drugs. Due to its important function in reabsorption of useful and secretion of harmful substances the proximal tubule, especially in its S3 segment, kidneys are susceptible to damage by various xenobiotics. Cisplatin is an important cytostatic used for the treatment of various malignant tumors. One of the main disadvantages of cisplatin is its nephrotoxicity. In the short term, cisplatin treatment leads to acute renal failure that causes various pathophysiological changes. In the long term there is a possibility of developing chronic kidney disease (CKD), in which kidney function progressively decreases. Kidney fibrosis is always present in CKD, and it is characterized by the accumulation and activation of fibroblasts and myofibroblasts. It is known that the process of epithelial-mesenchymal transition is involved in the formation of fibroblasts from tubular epithelial cells. NaK ATPase, a protein pump responsible for the active transport of sodium and potassium against the chemical gradient, is involved in this process. Here, using immunohistochemistry and western blot methods, I showed that there is a decrease in the expression of the alpha subunit of NaK ATPase at the protein level in rats, after single treatment with cisplatin. Increased expression of mRNA for the same protein, obtained by the RT-PCR method, is also visible.