Determination of The Properties of Rat Brain Thermostable Protein Complex which Inhibit Cell Proliferation

OBJECTIVES Cell proliferation is known to be controlled by many networks of regulatory proteins. These multiple and complicated mechanisms of control are still being investigated. The aim of the present study is to determine the different properties of adult rat brain thermostable protein complex (TPC) which affect cell proliferation. MATERIALS AND METHODS This experimental study used brain, kidney and liver tissue from adult (150-170 g) and adolescent (7, 10, 21, 28 days) white rats, adult pigeons and mice. Brain TPC was isolated by alcohol extraction, and primary antibodies Ki67 and GAD65/67 were used for immunohistochemistry, evaluation of transcriptional activity of the tissues and determination of the mitotic index. RESULTS The results show that brain TPC from rats reversibly decreases cell proliferation by inhibiting transcription. The evidence suggests that TPC is not species-specific, but expresses tissue specificity with regards to terminally differentiated cells. Rat brain TPC inhibits mitotic activity of the progenitor cells in the dentate gyrus of adolescent rats, and corresponding with this decrease in the mitotic index the number of Ki67 positive cells increases. Simultaneously, the number of GAD65/67-positive cells in the hippocampus decreases by approximately threefold. CONCLUSIONS These results indicate that rat brain TPC causes the reversible suppression of cell proliferation through the inhibition of transcription. Inhibitory effects of rat brain TPC leads to an increase the number of cells in the cell cycle, in tissues of adolescent rats.