The influences of spermine (SM) and DFMO. an irreversible ODC-inhibitor, on the polyamine metabolism, CK-activity, [^(3)H]-thymidine DNA synthesis, and isoactin mRNA expression of BC_(3)H1 in culture were studied, with the references of phosphodiesterase(PDE)-inhibitors including isobutyl-methylxanthine (IBMX) and KR30075.
BC_(3)Hl cells cultured in 10% fetal bovine serum (FBS)-DMEM for 24 hrs (the first : pre-drug phase) were cultivated in 10% FBS-DMEM added with one of the test drugs for further 96 hrs(the second proliferation phase), and then continue to grow in 2% FBS-DMEM for 48 hrs (the third : differentiation phase).
The putrescine content of BC_(3)Hl harvested after the first phase was relatively higher in comparison with those of the other phases and was gradually decreased through the full phases of culture, and the spermine content was little changed. The spermidine (SD) content was. unlike other polyamines, increased by 26.5% at the end of the second phase, but that SD increase was moderately attenuated by PDE-inhibitors, particularly KR30075, and furthermore. the SD content of BC_(3)Hl cultured in the presence of DFMO, unlike other polyamines. showed the marked and gradual decrease throughout the full phases of culture.
The [^(3)H]-thymidine DNA synthesis during the third : differentiation phase was not affected by IBMX and slightly inhibited by KR30075, but was significantly inhibited by SM plus DFMO or each of them.
And the creatine kinase (CK) activity gradually increased in advancing with culture duration was not changed by PDE-inhibitors. but both SM and DFMO significantly enhanced the increase of CK activity.
The synthesis of BC_(3)Hl α-actin and β-/ γ-actin mRNAs was significantly enhaced by DFMO, and the DFMO-induced enhancement was dramatically inhibited by SM. And PDE-inhibitors and SM little affected the synthesis of α-actin mRNA, but PDE-inhibitors attenuated the synthesis of β-/ γ-mRNAs, especially in the second phase.
These results suggest that polyamines have a pivotal role in the proliferation and differentiation of BC_(3)Hl cells, that the enhancement induced by DFMO of expression of VSM isoactin gene seems to be an attractive subject to be studied in future, and that PDE-inhibitors may inhibit the synthesis of VSM β-/ γ-actin mRNAs.
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