-transparent.png){kind=logo}
Kinetic experiments of labelling in vivo with [14C]orotate of cellular free UMP and/or UTP, nucleolar, nucleoplasmic and cytoplasmic rRNA in normal and 12 h-regenerating rat liver were performed. The specific-radioactivity curves obtained were analysed by computer and the rates of synthesis of precursor rRNA (45S pre-rRNA) and cytoplasmic 28S and 18S rRNA calculated. (a) The rates of synthesis of 45S pre-rRNA in normal and regenerating rat liver are 1400 and 3700 molecules/min per nucleus respectively; (b) the average rates of formation of mature 28S and 18S rRNA are identical with the rates of synthesis of 45S pre-rRNA in both normal and regenerating rat liver. Thus the synthesis of rRNA in 12h-regenerating rat liver is activated 2.7-fold. The analysis of rRNA synthesis in isolated nucleoli also shows a 2.7-fold stimulation of transcription in regenerating liver. It is concluded that all the 45S pre-rRNA molecules synthesized are processed and transferred as 28S and 18S rRNA in the cytoplasm, i.e. degradation (wastage) of newly synthesized ribosomes in the nucleus does not occur in both normal and regenerating rat liver. Thus the enhanced production of ribosomes in regenerating rat liver is regulated only at the transcriptional level.
M D Dabeva, and
K P Dudov
May 1972,
European journal of biochemistry,
M D Dabeva, and
K P Dudov
November 1969,
Biochimica et biophysica acta,
M D Dabeva, and
K P Dudov
January 1968,
The Journal of biological chemistry,
M D Dabeva, and
K P Dudov
January 1979,
Archives of toxicology. Supplement. = Archiv fur Toxikologie. Supplement,
M D Dabeva, and
K P Dudov
June 1990,
Gastroenterologia Japonica,
M D Dabeva, and
K P Dudov
February 1991,
FEBS letters,
M D Dabeva, and
K P Dudov
May 1994,
Hepatology (Baltimore, Md.),
M D Dabeva, and
K P Dudov
March 1981,
Cell,
M D Dabeva, and
K P Dudov
April 1968,
Journal of molecular biology,
M D Dabeva, and
K P Dudov
November 1994,
Biochemical and biophysical research communications,
