VEILLETTE, P.A.; GARCIA, M.M.; SPECKER, J.L.; University of Rhode Island: Immunolocalization of corticosteroid receptor with proliferating cell nuclear antigen and proton pump during stomach formation in metamorphosing summer flounder.

Formation of gastric glands is a hallmark of stomach development during larval metamorphosis of the gastric marine teleosts. Organogenesis occurs in an orderly progression of epithelial proliferation and differentiation in the incipient stomach. Invaginations of the surface epithelium will form the numerous gastric glands that secrete acid for digestion. Thyroid hormones drive flatfish metamorphosis (and stomach formation), although cortisol is thought to augment its actions. We report here, changes in immunoreactivity to a glucocorticoid-like receptor (GLR), proliferating cell nuclear antigen (PCNA), and the gastric proton pump (hydrogen/potassium ATPase beta-subunit) in the developing stomach of summer flounder (Paralichthys dentatus). Immunoreactivity to PCNA was wide-spread in pre-gastric surface epithelium and nascent gastric glands, indicative of proliferation. Proton pump-immunoreactivity appeared in gastric glands at later stages of differentiation, and was strongest in the post-metamorphic stage, evidencing a functional development of the glandular epithelium. GLR was strongly immunolocalized in surface epithelium and gastric glands throughout proliferative and differentiative stages of development. Staining of GLR was both nuclear and cytosolic in pre-gastric surface epithelium, but predominantly cytosolic thereafter. Localization of GLR in cell populations that sequentially express PCNA and the gastric proton pump provides correlative evidence for direct actions of cortisol during formation, and function, of the stomach. [Funded by NSF IBN-0220196]