Primary rat hepatocytes express cyclin D1 messenger RNA during their growth cycle and during mitogenic transitions induced by transforming growth factor-alpha.
Cyclin D1 messenger RNA expression was investigated in differentiated proliferation-competent primary cultures of adult rat hepatocytes. Periodic expression was observed during the 12-day growth cycle (approximately two population doublings). Upon reaching a quiescent G(o)-state, 4-kb cyclin D1 mRNA levels were undetectable. When G(o) cultures were shifted into defined media without or with 0.2-0.8 nM TGF-alpha, conditions that reinitiate full proliferative transitions synchronously, cyclin D1 mRNA levels were elevated 1.2-4.6-fold, respectively. These findings support the hypothesis that hepatic mitogens stimulate periodic cyclin mRNA expression directly.
Koch
K S
KS
Department of Pharmacology, University of California San Diego, La Jolla 92093.
Lu
X P
XP
Leffert
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HL
D000818:Animals; D015152:Blotting, Northern; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D019938:Cyclin D1; D016213:Cyclins / Q000096:biosynthesis*; D015870:Gene Expression / Q000187:drug effects; D007700:Kinetics; D008099:Liver / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D015513:Oncogene Proteins / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D051381:Rats; D011916:Rats, Inbred F344; D013997:Time Factors; D016211:Transforming Growth Factor alpha / Q000494:pharmacology*
D016213:Cyclins; D015513:Oncogene Proteins; D012333:RNA, Messenger; D016211:Transforming Growth Factor alpha; D019938:Cyclin D1