FEATURES OF ULTRASTRUCTURAL CHANGES IN THE KIDNEYS OF WHITE RATS DURING SUDDEN WITHDRAWAL OF DEXAMETHASONE AFTER ITS PROLONGED ADMINISTRATION IN HIGH DOSES

The aim of the research to determine the features of ultrastructural changes in renal hemocapillaries and renal tubular epithelial cells during prolonged administration of high doses of dexamethasone and after its sudden withdrawal.Material and methods. The study was conducted on white outbred sexually mature male rats, which were administered dexamethasone at a rate of 0.16 mg/kg for 28 days. After its withdrawal, morphological material was collected after 1, 3, 7, 14 and 28 days. Ultrastructural examination of the kidneys was performed according to general rules.Results. Sudden withdrawal of dexamethasone after its previous long-term administration in high doses at first (from the 1-st to the 7-th day) resulted in the gradual elimination of those morphofunctional vascular reactions and the state of epithelial cells of the proximal renal tubules dependent on them, which developed as a result of the drug's action with its long-term administration (decreased hemocapillary permeability, hydropic dystrophy of renal tubular epithelial cells). However, on the 14-th day after drug withdrawal, a pronounced decrease in blood flow was observed through significantly dilated renal hemocapillaries with simultaneous restoration and progression of dystrophic processes in renal tubular epithelial cells. Subsequently, by the 28-th day of the experiment, there is a reverse, almost complete restoration of the morphofunctional state of the ultrastructural components of the kidneys.Conclusions- Abrupt withdrawal of dexamethasone after prolonged administration in high doses initially promotes partial restoration of the ultrastructure of renal capillaries and renal tubular epithelial cells.- The 14th day is characterized by a sharp decrease in blood filling of hemocapillaries against the background of a noticeable expansion of their lumen with repeated progression of dystrophic processes in the epithelial cells of the renal tubules.- In the long term, there is a gradual, almost complete restoration of the morphofunctional state of the ultrastructural components of the kidneys due to adaptive and compensatory processes.