VEILLETTE, P.A.*; GARCIA, M.M.; HINKLE, L.; SPECKER, J.L.; University of Rhode Island; University of Rhode Island; University of Rhode Island; University of Rhode Island: Detection of Glucocorticoid-Like Receptor During Stomach Organogenesis in Summer Flounder

The stomach is an important organ, both physiologically and ecologically. Little is known about the endocrine regulation of stomach organogenesis. However, in vertebrates in general, corticosteroids and thyroid hormones significantly regulate development. In summer flounder, Paralichthys dentatus, stomach organogenesis occurs at the end of the larval phase during metamorphosis. In the incipient stomach, the developmental progression of proliferation, morphogenesis, and cell differentiation is closely associated with sequential amplification of cortisol and thyroid hormone. As one step in determining if the action of cortisol is necessary prior to thyroid hormone�s action during stomach organogenesis, we examined the spatial and temporal pattern of immunoreactivity for the glucocorticoid-like receptor (GLR). The antiserum was raised against a synthetic peptide for human glucocorticoid receptor. A specific immunoreaction was seen in chloride cells of the gills, pseudobranch, intestine, kidney tubules, and stomach. In the fully differentiated stomach of post-metamorphic juveniles, there was strong GLR immunoreactivity specifically localized in the gastric epithelium and gastric glands. This strong immunoreaction was corroborated by northern blot analysis, in which mRNA expression was similar to that for gills and intestine. Most importantly, GLR immunoreactivity was observed in the incipient stomach at developmental stages as early as pro-metamorphosis (immediately prior to metamorphic stages), the time when whole-body cortisol concentrations peak, consistent with a role for cortisol in stomach organogenesis of summer flounder. [Supported by NSF IBN-0220196]