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RNA Synthesis in Ascites Hepatoma AH-130 Cells of Rats¹

Biology Division, National Cancer Center Research Institute, Tsukiji, Chuo-ku, Tokyo, Japan

The cellular components that were isolated from Ascites Hepatoma AH-130 cells were cytoplasm, nuclei, chromatin, nuclear sap, and nucleoli. The RNA/DNA ratio of isolated nuclei was 0.36. The isolated nucleoli contained about equal amounts of RNA and DNA. The nucleus of the hepatoma cells contained more RNA than the normal rat liver cell nucleus, especially in the nucleolus.

The RNA's were extracted from these cellular components, and their sedimentation classes were determined by sucrose density gradient centrifugation and by their nucleotide composition. RNA sedimenting faster than 28 S ribosomal RNA was detectable in the nucleoli. In the chromatin and nuclear sap fraction, small but significant amounts of RNA of an intermediate molecular size, between 18 S and 4 S, were found, as well as ribosomal and soluble RNA's.

Newly synthesized RNA in the nucleolus was the guanosine-cytosine-rich ribosomal-type RNA, with a sedimentation coefficient greater than 28 S. On the other hand the RNA synthesized in the chromatin fraction was adenosineuridine rich.

About 50 and 36% of the newly synthesized RNA were found in nucleoli isolated from 5-day-old and 7-day-old ascites hepatoma cells, respectively. These results indicate that ribosomal RNA synthesis was very active in the rapidly proliferating hepatoma cells.

¹ This work was supported by a grant-in-aid for special project research on biophysics from the Ministry of Education of Japan.

Received 11/29/68. Accepted 4/17/69.