The influence of pineal factors on the bone marrow cell profile in animals of different ages during changes of the thymus functional condition

Abstract

The role of thymus on the effects of a pineal body on the number of stromal fibroblast colony-forming units (CFU-F), granulocyte and macrophage colony-forming units (CFU-GM), as well as CD3+-, CD4+-, and CD8+-cells, in the bone marrows of adult and old CBA/Ca mice was studied. Thymectomized and sham-operated mice received either melatonin in the evening (during spring) or epithalamin in the morning (during summer and autumn). After the administration of melatonin, the CFU-F/CFU-GM ratio decreased in adult sham-operated animals, and increased in adult animals after thymectomy. Melatonin induced an increase of the CD4+/CD8+ ratio in mice with an intact thymus and a decrease in mice after thymectomy due to the increase of number of CD8+-cells. Epithalamin caused the increase of the number of CFU-F in the summer but not in the autumn; this effect was less prominent in mice after thymectomy. The changes of the studied parameters under the influence of pineal factors in adult mice with an intact thymus correspond to their seasonal fluctuations. After administration of melatonin, the CFU-F/CFU-GM ratio slightly decreased in old sham-operated animals, and did not change in animals after thymectomy. The CD4+/CD8+ ratio in old mice slightly increased under the effect of melatonin, regardless of the presence or absence of thymus. Thus, in adult mice, the effect of pineal factors (melatonin, epithalamin) on the cell profile of bone marrow, and particularly on the cells of the microenvironment, is adaptive and involves thymus. In old mice, thymus is also involved in the effects of melatoninon on bone marrow, however, its influence is less pronounced and mostly appears as a change of the CFU-GM.