Introduction. Melanoma is one of the most malignant human tumors, originating from melanin-forming tissue. Currently, among the risk factors for the development of malignant neoplasms, including melanoma, light pollution is considered – exposure to light at night. In turn, the violation of circadian rhythm under conditions of light pollution often leads to the occurrence of desynchronosis, which is the cause of the development of a number of diseases, including malignant neoplasms. As a rule, light pollution is accompanied by a decrease in the production of epiphyseal melatonin, which has oncostatic, antitumor and antioxidant effects.The objective of study was to study the morphological features of transplanted B16 melanoma, to establish the micromorphometric indicators of tumor cells and circadian rhythms of some of them for further use as control indicators in the study of the effect of various light regimes and experimental therapy on the morphofunctional state of the body of animals with transplanted melanoma.Methods and materials. The study was conducted on male hybrid mice of the BDF1 line. The animals were divided into 2 equal groups of 25 individuals. The first group served as an intact control, the mice of the second group were transplanted with B16/F10 melanoma. On the 15th day after tumor inoculation, the animals were withdrawn from the experiment at 9.00, 15.00, 21.00 and 3. The mass and volume of the tumor were determined, microscopic, including micromorphometric studies of tumors were performed. Glucose levels were determined in blood plasma. The daily dynamics of the studied parameters was assessed, and for the statistical calculation of the amplitude and acrophase of circadian rhythms, a cosinor analysis was performed.Results. The study of the circadian rhythm of glucose made it possible to reveal its difference in animals with melanoma from that in the control. Changes in the daily rhythmicity of this metabolite, which comprehensively reflects the synchronization of many rhythms with each other, allows us to state a significant change in circadian rhythmostasis in animals with melanoma. As a result of the study, we have established micromorphometric indicators characteristic of B16 melanoma on the 14th day after transplantation. The circadian rhythm of the area of the nucleus and cells, the mitotic index and the absence of a clock for the NCR were established. The difference between the phase-amplitude features of the CR of the area of the nucleus of melanocyte cells from the normal ones was found.Conclusion. The obtained data indicate a change in rhythmostasis in mice with experimental B16 melanoma. The features of the organization of the rhythmicity of the tumor itself can be used in its targeted experimental therapy, taking into account chronobiological features. The results of the study can be used for further studies of the effect of various lighting modes on the morphofunctional state of the animal organism in the pathology under study.
