Abstract: The objective of this study was to investigate the effects of L-arginine on feed intake, gastrointestinal hormone secretion and gene expression of calcium-sensing receptors (CaSR) in rats. Two experiments were conducted. In experiment I, thirty-two male Sprague-Dawley (SD) rats were randomly divided into 4 groups: a control group (oral gavage 0 mmol·kg^-1 L-Arg·HCl), a low dose group (5 mmol·kg^-1 L-Arg·HCl), a medium dose group (10 mmol·kg^-1 L-Arg·HCl) and a high dose group (20 mmol·kg^-1 L-Arg·HCl). The feed intake was recorded at different time points after gavage, and the indicated dose of L-Arg·HCl was chosen for the experiment II based on feed intake. In experiment II, thirty male rats were divided into two groups: a L-Arg·HCl treatment group (20 mmol·kg^-1) and a control group (0 mmol·kg^-1). The corresponding solution was gavaged once a day consecutively for one week. During this period, daily feed intake and changes in body weight were recorded. At the end of the experiment, all rats were euthanased. The venous blood, stomach and small intestine tissue, and hypothalamus were collected for the analysis of gastrointestinal hormones, and gene expression of the CaSR, neuropeptide Y and proopiomelanocortin (POMC) levels. In experiment I, compared with the control group, the concentrations of L-Arg·HCl at 10 and 20 mmol·kg^-1 reduced food intake for 0-1 and 0-24 h, respectively, after gavage (P<0.05), with the greatest reduction in feed intake occurring at 20 mmol·kg^-1. In experiment II, after being orally gavaged with 20 mmol·kg^-1 L-Arg·HCl for 1 week, the body weight gain and cumulative feed intake in the first two days were decreased (P<0.05), while the secretion of cholecystokinin (CCK), expression of CaSR and POMC were up-regulated (P<0.05). However, the secretion of gastrin and glucose-dependent insulinotropic peptide (GIP) was not significantly affected, but did show an increasing trend. A correlation analysis suggested that the concentration of CCK in serum had a significant positive correlation with the gene expression level of CaSR in the duodenum, jejunum and with hypothalamic POMC (P<0.05), while the concentration of GIP in serum had a positive correlation with the expression level of CaSR in the duodenum and POMC in the hypothalamus (P<0.05). Meanwhile, the concentration of glucagon-like peptide-1 in serum displayed a trend towards positive correlation with the gene expression level of CaSR in jejunum and POMC in the hypothalamus (0.05<P<0.1). These results suggest that L-Arg may reduce feed intake of rats by up-regulating the expression of CaSR, increasing the secretion of gut satiety hormones, and up-regulating the expression of the anorexia factor POMC.

Key words: rat, L-Arg, calcium sensing receptor, gut hormone, feed intake