ATP

As a-endosulfine represents a putative ligand of KATP and KATP are present in MC, we postulated that a-endosulfine was expressed in the rat kidney in vivo and in cultured rat MC in vitro. We determined that ENSA was expressed abundantly in rat kidney by in situ hybridization. Further observations, utilizing Northern blotting and RT-PCR, established a-endosulfine message in cultured MC in vitro and in whole rat kidney in vivo, with expression predominantly localized to the glomeruli. Further studies of a-endosulfine expression by immunoblotting and confocal microscopy confirmed its presence in vitro and in vivo.

ENSA gene and protein expression in MC is altered in response to a hyperglycemic milieu. Cultured cells increased ENSA gene expression by twofold following exposure to 30 mM glucose within 24-48 h, and this effect persisted for at least 10 d, even after withdrawal of the inciting stimulus (53). Thus, MC expression of SUR2B, Kir 6.1 and a-endosulfine lays the foundation for the existence of a regulatable intracellular KATp/endosulfine receptor/ligand system, which could influence MC contractility and matrix metabolism (54).

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