Objective       To determine the protective effect of tannic acid (TA) on megakaryocytes against ionizing radiation and investigate its underlying mechanism.       Methods       Human megakaryoblast M07e cells were pretreated with TA at concentrations of 0

0.5

1

2.5

5 and 10 μg/mL before receiving 10 Gy γ-ray irradiation. The cell viability

levels of reactive oxygen species (ROS)

mitochondrial membrane potential (MMP) and apoptotic rate of the cells were detected after ir

radiation. Subsequently

BALB/c mice with or without TA treatment were irradiated with

60

Co γ at a dose of 5 Gy

and the blood platelet count and number of megakaryocytes in bone marrow were determined at appointed time points.       Results       TA dose-dependently improved the survival rate of M07e cells after irradiation. Compared with control group

TA significantly reduced the intracellular ROS levels (P0.05)

improved MMP (P0.05) and decreased the apoptotic rate (P0.05) in M07e cells after irradiation. In vivo

TA pretreatment resulted in a significant increase in the number of megakaryocytes in bone marrow in BALB/c mice after irradiation. Meanwhile

the blood platelet counts in TA treated mice were much higher than those in the control group

especially at days 7

12

15

and 19 after irradiation (P0.05

P0.01).       Conclusion       TA has a protective effect on megakaryocytes against ionizing irradiation

possibly via its inhibition on radiation-induced oxidative stress.