Comparison of low voltage amplitude electrochemotherapy with 1 Hz and 5 kHz frequency in volume reduction of mouse mammary tumor in Balb/c Mice

  Introduction: Electrochemotherapy (ECT) is an efficient technique that high intensity electric pulses in combination with chemotherapeutic drugs are applied to tumor cells. The most important unpleasant sensation of electrochemotherapy is muscle contraction. To resolve this problem, there are two solutions: first, increasing the repetition frequency of electric pulses above the tetanic frequency and, second, reducing the voltage amplitude. ECT using 1 Hz or 5 kHz frequency at high amplitude examined and no difference response of the tumor treatment was observed. But the role of frequency in low amplitude ECT not examined. Therefore, the present study compared the anti-tumor effectiveness of electrochemotherapyusing electric pulses with frequencies of 1 Hz and 5 kHz at 70 v/cm amplitude.   Materials and Methods: ECT of spontaneous mouse mammary tumor (SMMT) transplanted in Balb/c was performed with intratumoral injection of bleomycine and applied four different electric pulse protocols: 1- a train of 8 pulses with duration 50 ms, 1 Hz frequency and 70 v/cm amplitude, 2- a train of 4000 pulses with duration 100 µs, 5k Hz frequency and 70 v/cm amplitude,3- a train of 8 pulses with duration 100 µs, 1 Hz frequency and 1000 v/cm amplitude,4- a train of 8 pulses with duration 100 µs, 5 kHz frequency and 1000 v/cm amplitude.   Results : Our data demonstrate significant differences in tumor volumes between mice treated by 70 V/cm and 5 kHz frequencycompared to1 Hz frequency but inhibited tumor growth in high amplitude with 1 Hz and 5 kHz is comparable. Based on these results, the pulses with 70 v/cm and 5 kHz frequency are most effective. Conclusion: On the basis of these results the frequency effect of electric pulses is important in low amplitude ECT