Cellular and nuclear volume of human cells during the cell cycle

The volumes of whole cells and nuclei of cultured human cells were studied at different times after synchronization of growth using the Coulter counter and scanning microphotometry. It was found that the increase in cell volume is compatible with both linear or exponential growth during the cell cycle. The growth of the nuclear volume is not correlated with the beginning of the DNA synthesis. The nuclear volume starts to increase already 6 hr prior DNA synthesis. The data also indicate that the nuclear volume growth could proceed in two stages. The relation of this result to radiation sensitivity is discussed.