Localization of sulphonylurea receptor proteins SUR2A and SUR2B and/or SUR1 in rat kidney

ABSTRACT

To further explore precise expression and localization of sulphonylurea receptor isoforms SUR2A and SUR2B [SUR1] in rat kidney, total RNA was isolated from the kidney tissue using the TRIzol kit. Three different primer sets designed against SUR isoforms were used in reverse transcriptase reactions. Western blotting was done on membrane fractions obtained from kidney tissues using the primary antisera for SUR2A and SUR2B [SUR1]. Paraformaldehyde fixed kidney sections were immunostained with SUR2A and SUR2B [SUR1] primary antisera. Sections were developed with DAB as a chromogen. RT-PCR results demonstrated mRNA consistent with SUR1 isoform to be the only identifiable transcript. Western blotting could not identify any protein consistent with SUR2A or SUR2B [SUR1] but recognized instead a smaller 55kD protein of unknown identity. Immunohistochemistry demonstrated a differential staining pattern whereby SUR2A was localized to the mesangial cells, intra- and extrarenal blood vessels and smooth muscles. In contrast, SUR2B [SUR1] was localized only to distal nephron epithelia. Intense immunoreactivity was localized to the thick ascending limb and as well as in the outer and inner medullary collecting ducts, both. Our results demonstrate differential and highly localized expression pattern of sulphonylurea receptor proteins SUR2A and 2B [SUR1] in rat kidney with implications for drug design: