2.8. Reverse transcription-polymerase
chain reaction (RT-PCR) Cells grown in 100-mm tissue culture dishes to about 80% confluency in DMEM supplemented with 10% FBS. After washing twice with PBS, the cells were cultured for 12 or 24 h in FBS-free DMEM, together with the indicated concentrations of A. radix extract. Total RNA samples were extracted by acid using the guanidinium thiocyanate, phenol— chloroform method [22]. One microgram of total RNA samples were reverse-transcribed using the Reverse Transcription System (Promega). The RT products were then subjected to PCR cycles as follows: of 94 8C for 1 min, 58 8C for 1 min, and 72 8C for 1 min for 33 cycles. The primers used for amplifying the respective fragments are listed in Table 1. After agarose gel electrophoresis, the PCR products were quantified using a densitometer
(Imagemaster, Pharmacia Biotech).