The expression of cAMP-dependent protein kinase subunits is differentially regulated during liver regeneration.
The levels of the regulatory (RI and RII) and catalytic (C) components of cAMP-dependent protein kinase and of their messages were studied during the first 36 h of liver regeneration after 70% hepatectomy. Both RI alpha mRNA and RII alpha mRNA started to increase 4 h after the resection, reaching peak levels after 9 h. RI mRNA decreased abruptly 9-12 h after resection, whereas RII mRNA stayed elevated. C alpha mRNA was rather constant during the period of study. In accordance with the mRNA data the level of C was constant while RI and RII increased during the prereplicative phase of liver regeneration. RI increased rapidly when its message became elevated. RII, however, increased noticeably only 6-8 h after its mRNA had become elevated. The increased expression of R led to a disproportion between R and C that was most pronounced 14 h after resection, i.e. coinciding with the prereplicative cAMP burst. The increased R/C ratio at that time of regeneration diminished the concentration of active C subunit during the cAMP burst. In that way the otherwise inhibitory effect of high concentrations of active C on the DNA replication may have been decreased. The fractional saturation of RI and RII by endogenous cAMP fluctuated in parallel as a function of liver cAMP levels, although there was a tendency that RI was more highly saturated than RII at high concentrations of cAMP.
Ekanger
R
R
Department of Anatomy, University of Bergen, Norway.
Vintermyr
O K
OK
Houge
G
G
Sand
T E
TE
Scott
J D
JD
Krebs
E G
EG
Eikhom
T S
TS
Christoffersen
T
T
Ogreid
D
D
Døskeland
S O
SO
D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism / Q000494:pharmacology*; D003600:Cytosol / Q000201:enzymology; D004261:DNA Replication; D005786:Gene Expression Regulation; D006498:Hepatectomy; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008115:Liver Regeneration; D046911:Macromolecular Substances; D008297:Male; D009693:Nucleic Acid Hybridization; D011494:Protein Kinases / Q000096:biosynthesis / Q000235:genetics*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D011919:Rats, Inbred Strains
D046911:Macromolecular Substances; D012333:RNA, Messenger; D000242:Cyclic AMP; D011494:Protein Kinases