Effects of l-arginine on growth hormone and insulin-like growth factor 1.

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.