The Inhibitory Effect of Iodoacetamide on Recovery from Sub-lethal Damage inChlamydomonas Reinhardti

Abstract

Recovery of x-ray induced sub-lethal damage in synchronized cultures of Chlamydomonas reinhardti, studied by the dose fractionation technique, is accompanied by an increase in D₀ of the recovered cells. The values of D₀ after the acute and fractionated doses (fractionation interval 200 min) are 2550 and 7090 rads, respectively. Iodoacetamide (IOAM) when present during irradiation at the concentration of 1 × 10⁻⁴ M sensitizes C. reinhardti to x-rays. This effect is about three times higher in the recovered cells after the test dose given in the presence of IOAM. The resulting D₀ has the same value (1600 rads) as after the acute dose given in the presence of IOAM. Incubation of irradiated cells with IOAM during the fractionation interval, sufficiently long for complete recovery, causes inhibition of the recovery mechanisms. The fact that, in normal as well as in recovered cells, IOAM reduces D₀ to the same value, is also considered to be a result of inhibition of the repair mechanisms.