Simple method for extracting RNA from cultured cells and tissue with guanidine salts

We have developed a simple protocol for isolating RNA from both cell culture and tissue from human and animal sources, using guanidine thiocyanate and guanidine hydrochloride, but no organic solvents. The protocol reproducibly yielded 15 to 25 micrograms of high-quality RNA per 10(6) cells of human and animal origin and 1 to 1.1 mg of RNA per gram of human placental tissue. The RNA so obtained was ribonuclease-free and not contaminated by DNA. It was suitable for reverse transcription-polymerase chain reaction, Northern blot analysis, and in vitro expression of proteins. Thus, the molecular assessment of both research and clinical samples can be readily and reliably initiated by the application of this protocol.