Figure 4.

Polyamine deficiency results in H₂O₂ hypersensitivity. HT306 cells were grown in amine-deficient VB medium to deplete cellular amines. The cultures were diluted 1:50 and divided into two parts. To one part of the culture, a mixture of 10⁻⁵ M of spermidine and 10⁻⁴ M of putrescine was added; to another part, no amines were added. The cultures were grown overnight to an OD₆₀₀ of 0.15–0.20, the cells were washed twice and resuspended in K-PO₄ buffer (pH 7), and different concentrations of hydrogen peroxide were added. Periodically, aliquots were taken for viable cell counts. The data are plotted as the percent survival after the H₂O₂ treatment; the initial cell count was 1.1 × 10⁸ cells per ml.