Table 1.

rRNA synthesis in asynchronously growing U2OS and SAOS‐2 cells treated with ActD, measured by the evaluation of [3H]‐uridine radioactivity (d.p.m./µg RNA) incorporated in the RNA fraction extracted at 50 °C (precursor rRNA)

Cell line	Untreated cells	ActD for 1 h and immediately processed	ActD for 1 h and processed 7 h after drug removal	ActD for 1 h and processed 13 h after drug removal
U2OS (mean ± SD)	6782 ± 274	2746 ± 99*	3046 ± 175*	4731 ± 157*
SAOS‐2 (mean ± SD)	3131 ± 243	1310 ± 36*	1317 ± 143*	2541 ± 62**

^* P < 0.0001 and

^** P < 0.01, referred to untreated cells.