Gastric immunolocalization and plasma profiles of acyl ghrelin in fasted and fasted-refed prepuberal gilts.

Ghrelin is a peripheral circulating hormone, mainly released from the stomach, which can stimulate food intake. We studied fed, fasted, and fasted-refed prepuberal gilts, in order to outline possible changes in gastric mucosal ghrelin cells and in plasma ghrelin profiles in reponse to food deprivation. Acyl-ghrelin-immunoreactive cells were numerous in oxyntic glands, less abundant in cardiac and least frequent in pyloric glands, with the addition of a minor population of labelled cells in the gastric pit mucosa. When fed and fasted animals were compared (72 h fast vs. fed; n=4+4), no clear-cut differences were revealed in labelled cell numbers, nor in their staining intensity. A radioimmunoassay for plasma porcine acyl-ghrelin (n-octanoylated at Ser3), not recognizing des-acyl ghrelin, was validated. Plasma acyl-ghrelin progressively increased upon fasting (over 6, 12, 24 and 48 h); ghrelin levels significantly (p<0.05) higher than those pre-fast were reached at 72 h. After refeeding, plasma ghrelin was rapidly restored to basal values by 6 h. In the same animals, plasma insulin was significantly reduced throughout the fasting period (6-72 h), while rapidly increasing after re-feeding. NEFA levels increased during fasting (12-72 h) and rapidly returned to low values after re-feeding. In conclusion, the present study demonstrates that starvation and refeeding influence ghrelin plasma level in prepuberal gilts. The absence of detectable changes in ghrelin cells, as seen in immunohistochemistry, could be due to a large intracellular storage of potentially releasable acyl-ghrelin