l-Arginine has been reported to promote cellular and organismal growth. In this study, the effects of l-arginine on the expression of growth hormone (GH) and insulin-like growth factor 1 (IGF-1), the two key growth factors, are investigated in cultured GH3 pituitary epithelium and HepG2 cells, respectively. l-Arginine significantly induced the gene expression of GH and IGF-1 in GH3 pituitary epithelium and HepG2 hepatocytes respectively, and reduced IGF binding protein-1 gene expression in HepG2 cells assessed via quantitative polymerase chain reaction analysis. l-Arginine also significantly induced GH and IGF-1 hormone secretion from GH3 and HepG2 cells, respectively. In addition, the multi-target ELISA analysis conducted revealed that phosphorylation of p-38 MAPK, MEK, and JNK were significantly increased in HepG2 cells, suggesting l-arginine-induced activation of the MAPK signaling pathway. These results suggest that l-arginine promotes the synthesis and secretion of GH and IGF-1 in vitro and induces the MAPK signaling cascade in cultured hepatocytes.

The effects of the ethanolic extract of brown rice (BRE, L. cv. Hiami) on cellular growth were investigated. Gene expression analysis by qPCR showed that the expression of the mRNA expressions of growth hormone (GH) and insulin-like growth factor (IGF)-1 genes was significantly induced in cells stimulated with BRE compared with controls, and the effects were dose dependent. In addition, the hormone secretion of GH and IGF-1 was significantly induced in GH3 and HepG2 cells stimulated with BRE in line with the qPCR results. Collectively, these results suggest that BRE induces the expression and secretion of GH and IGF-1; therefore, application may promote cellular growth.

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