Differential immunolocalization of sulfonylurea receptors in mouse and rat ureters

The receptors for sulphonylurea (SURs) are known to be expressed in the mouse kidney, but their expression in the ureter is undefined. Owing to the physiological and pharmacological significance of SURs, the localization of SUR in ureters of adult mice and rats was investigated through immunohistochemistry. Animals were perfused transcardially with 4% paraformaldehyde and tissues were processed for immunohistochemistry using polyclonal antisera against SUR2A and SUR2B (SUR1) receptor proteins. Sections were incubated with primary and secondary antisera and developed with aminoethylcarbazole as a chromogen. A differentiated localized staining pattern of SUR proteins in rat and mouse ureters is demonstrated. In the mouse, immunoreactivity of SUR2A was predominantly confined to the cytoplasmic portion of epithelial cells and blood vessels, with comparatively low-level staining found in smooth muscle. In contrast, SUR2B (SUR1) immunoreactivity was absent in mouse ureters. In rats, SUR2A immunoreactivity was localized only in the blood vessels, while SUR2B (SUR1) immunoreactivity was localized in the epithelial cell cytoplasm. Tissue specificity of SUR is demonstrated in the two species of rodents and suggests a role of SUR proteins in urinary metabolism pertaining possibly to salt handling and maintenance of the smooth muscle tone.