Glucagon receptor expression and glucagon stimulation of ghrelin secretion in rat stomach.

The present study was performed to evaluate the role of glucagon in the regulation of ghrelin secretion from the rat stomach. mRNA for ghrelin and glucagon receptor was expressed predominantly in the lower body and pylorus of stomach, but little or not in the upper body and cardia. Ghrelin- and glucagon receptor-immunoreactive cells were detected in lamina propria mucosae of stomach and some cells expressed both. Intravenous administration of glucagon caused transient increases in both acyl- and desacyl-ghrelin levels in the gastric vein within 10 min, which was followed by gradual increases in desacyl-ghrelin levels until 60 min. Steady state levels of ghrelin mRNA in the stomach were increased by 1.9-fold 20 min after glucagon administration, but not at 5 or 120 min. These results suggest that glucagon stimulates acute release of both forms of ghrelin and thereafter upregulates synthesis and release of desacyl-ghrelin in the rat stomach.