The effect of zinc, an essential trace element, on insulin-like growth factor-I (IGF-I) and transforming growth factor-β1 production was investigated to determine the role of this metal in bone growth of newborn rats. Femoral-diaphyseal and metaphyseal tissues were obtained between 1 and 28 days after birth of newborn rats, and cultured for 24 h in a serum-free Dulbecco's modified Eagle's medium containing either vehicle or zinc sulfate (10-6-10-4 M). Protein concentration in the medium was significantly increased by culture with bone tissues of newborn rats with increasing age (14 and 21 days). Medium IGF-I and TGF-β1 concentration was gradually reduced with increasing age after birth. The presence of zinc (10-5 and 10-4 M) caused a significant increase in protein, IGF-I, and TGF-β1 concentrations in the medium cultured with the diaphyseal or metaphyseal tissues obtained at 7 and 14 days after birth. The expression of IGF-I and TGF-β1 mRNA was demonstrated by reverse transcription-polymerase chain reaction (RT-PCR) analysis in the diaphyseal and metaphyseal tissues cultured for 24 h using rat IGF-I or TGF-β1-specific primers. These expressions were significantly raised in the presence of zinc (10-4 M) in culture medium. The present study demonstrates that zinc has a stimulatory effect on IGF-I and TGF-β1 production in the femoral tissues with bone growth of newborn rats.

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