[Effects of insulin-like growth factor II on regulating nitric oxide synthase gene expression in mouse osteoblast-like MC3T3-E1 cells].
OBJECTIVE
To study the effects of insulin-like growth factor II (IGF-II) on regulating the levels of nitric oxide (NO) and the mRNA transcriptions of inducible nitric oxide synthase (iNOS) and endothelial NOS (eNOS) in mouse osteoblast-like cells.


METHODS
Mouse osteoblastic cell line MC3T3-E1 was selected as the effective cell of IGF-II. After the cells were treated with IGF-II at different concentrations for different intervals of time, MTT colorimetry was used for examining the cell proliferation. Nitrate reductase method was applied for detecting the NO concentrations in cell culture supernatants and RT-PCR employed for determining the levels of cellular iNOS and eNOS mRNAs.


RESULTS
After the MC3T3-E1 cells were treated with IGF-II at the dosages of 1 microg/L for 72 h, 10 and 100 microg/L for 24, 48 and 72 h respectively, all the MTT values increased markedly (P < 0.05 or P < 0.01). After the cells were treated for 48 and 72 h at the dosage of 100 microg/L IGF-II respectively, the levels of NO in the supernatants of cell cultures and cellular iNOS mRNA decreased significantly (P < 0.01). However, the levels of eNOS mRNA in the cells treated with any of the IGF-II dosages for the different times were stable (P > 0.05).


CONCLUSIONS
IGF-II at the dosages of 1 approximately 100 microg/L showed the effects on promoting proliferation, which as probably due to the maintenance of low NO levels. Inducible NOS gene expression at the level of transcription was down regulated in the MC3T3-E1 cell treated with higher dosage of IGF-II (100 microg/L) but eNOS mRNA was not, which might be one of the mechanisms for the maintenance of low NO levels.
Sun
Wei-lian
WL
Department of Stomatology, The Second Affiliated Hospital, College of Medical Science, Zhejiang University, Hangzhou 310009, China.
Chen
Li-li
LL
Yan
Jie
J
Yu
Zhong-sheng
ZS
D016475:3T3 Cells; D000818:Animals; D007335:Insulin-Like Growth Factor II / Q000494:pharmacology*; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000096:biosynthesis* / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D012333:RNA, Messenger / Q000096:biosynthesis
D012333:RNA, Messenger; D009569:Nitric Oxide; D007335:Insulin-Like Growth Factor II; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496317:Nos2 protein, mouse; C496315:Nos3 protein, mouse