Immediate and short-, mid- and long-term effects of in vivo ionizing radiation exposure in BALB/c mice: II. activation of phorbol myristate acetate and/or calcium ionophore on lymphocyte proliferation.

AIM: To study the effects of whole-body irradiation (WBI) on lymphocyte proliferation at different times (0, 7, 15, 30, 90 and 180 days) in an animal sensitive to radiation, BALB/c-mice.
MATERIALS AND METHODS: Mice were irradiated (4 Gy) and euthanized at different times, and lymphocytes underwent different treatments: quiescent cells were cultured with calcium ionophore (5 min or 48 h) with/without phorbol myristate acetate (PMA). Lymphocytes were cultured with mitogens and underwent the same treatment. Cell proliferation was measured by a tritiated thymidine assay.
RESULTS: The results obtained varied at different time points: at 15 days post-irradiation, quiescent cells and PMA-treated cells showed a significantly decreased proliferation, but increased at 90 days; moreover, when cells were treated with ionophore, a significant stimulation was noted at all times. When cells were exposed to mitogens, they behaved according to its nature: thus, concanavalin A (ConA) and phytohaemaglutinin A (PHA) behaved differently with PMA, while lipopolysaccharide (LPS) had an inhibitory effect at 30 days post-irradiation, and pokeweed (PWM) stimulated proliferation at both 90 and 180 days. Accordingly, there were very few variations in the test results when mitogen concanavalin A (ConA) and calcium ionophore with/without PMA were used.
CONCLUSION: Our model is based on BALB/c mice. Cells induced to proliferate by the PKC enzyme and calcium ionophore are more resistant to irradiation than the same cells treated with specific T- and B-cells mitogen.