Folate deficiency followed by ionizing radiation perturbs hepatic dihydrofolate reducatse activity.

There is lot of interest in the folate metabolism because of the essential role of folate coenzymes in nucleic acid synthesis. Gamma (gamma) radiation is well known for inducing damage in the DNA. To counteract these damage, a variety of DNA repair pathways have evolved that require regular supply of DNA bases whose biosynthesis in turn depends on sufficient pools of folate dependent enzymes like dihydrofolate reductase (DHFR). In the present study, we examined the ionizing radiation mediated perturbation of DHFR activity in folate deficient and folate sufficient conditions. In folate deficient animals a potent inhibition of liver DHFR activity was observed. Our results showed that combination of folate starvation and ionizing radiation might adversely affect the DHFR activity, compared to their individual treatments. Measurement of apurinic/apyrimidinic sites (AP sites), a major type of DNA damage generated by radiation induced loss of purine and/or pyrimidine base, indicated a dose dependent DNA damage in folate deficient animals. In conclusion our data suggest an interactive role of folate deficiency and radiation injury in inhibiting DHFR activity.