EFFECT OF FASTING AND REFEEDING ON PLASMA GHRELIN LEVELS IN PREPUBERTAL GILTS

Ghrelin, a novel endogenous ligand for GH secretagogue receptor, has been recently isolated from the stomach. Its administration to rodents and humans stimulates GH secretion, increases food intake and reduces fat utilization. Recent studies in rodents suggest that ghrelin is involved in energy homeostasis and is influenced by nutritional status; however, scarce information is available about blood ghrelin levels in domestic animals. The aim of this study was to evaluate the effects of fasting and refeeding on plasma ghrelin levels in gilts. Eight prepubertal, ovariectomized gilts were fitted with an indwelling jugular catheter under general anesthesia. Two days later the gilts were bled every hour for a 4 h period during normal alimentation (time 0); after that, the gilts were fasted for 72h with free access to water. During this period, blood samples were collected at 6, 12, 24, 48 and 72 hours of fasting. After fasting, the animals were refeed and blood samples were collected each hour for an additional 4h period. After appropriate treatment with EDTA and aprotinin, acidified plasma samples were assayed for ghrelin concentrations by RIA using a polyclonal antibody specific for the N-terminal portion of human ghrelin, known to represent the active circulating form of the hormone. The antibody has been recognized to react also with porcine acylated portion of ghrelin. The assay was validated by verifying the parallelism of dilutions of plasma samples with the standard curve. Ghrelin plasma levels before fasting were 115.34+/-5.92 pg/ml. Throughout fasting they progressively increased to reach the highest concentrations at the end of fasting (163.9+/-10.42 pg/ml; P<0.05 vs pre-fasting values); after refeeding, ghrelin returned to basal levels by 4 h. On the basis of these results, we may hypothesize that ghrelin plays a role in long-term feed intake regulation.