Objective - to study structural changes in mast cells of rat testes of in response to exposure to stressors of different intensity. Material and methods. Testes were studied of 20 adult male Wistar rats, subjected to stressful influence of physical loads of different intensity. Mast cells numbers in the testes, their synthetic and functional activity were measured. At the same time, spermatogenesis activity was evaluated on the basis of several criteria. Results. Loads of moderate intensity had no effect on the morpho-functional state of testicular mast cells and didn’t not lead to any disurbances of spermatogenesis, indicating the appearance of training adaptive response. Prolonged exercises of high intensity lead to a decrease in the number of mast cells, reduction of their synthetic activity. Short-term loads of maximum intensity resulted in the decrease of mast cell functional activity. Conclusions. Loads of high and maximal intensity caused changes in morphological and functional parameters of mast cells in the testes of male rats and impeded normal functioning of the seminiferous tubules, providing an inhibitory effect on their sexual function.