Trafficking of ENaC subunits in response to acute insulin in mouse kidney
2007 (English)In: American Journal of Physiology - Renal Physiology, ISSN 0363-6127, E-ISSN 1522-1466, Vol. 293, no 1, F178-F185 p.Article in journal (Refereed) Published
Studies done in cell culture have demonstrated that insulin activates the epithelial sodium channel (ENaC) via a variety of mechanisms. However, to date, upregulation of ENaC in native renal tissue by in vivo administration of insulin has not been demonstrated. To address this, we injected 6-mo-old male C57BL/CBA mice (n = 14/group) intraperitoneally with vehicle or 0.5 U/kg body wt insulin and examined short-term (1-2 h) sodium excretion and kidney ENaC subunits (alpha, beta, and gamma) and serum and glucocorticoid-induced kinase (SGK-1) regulation. Insulin resulted in a significant reduction in urine sodium (by approximately 80%) that was restored by intraperitoneal administration of the ENaC antagonist, benzamil (1.4 mg/kg body wt). Differential centrifugation followed by Western blotting of whole kidney revealed significantly increased band densities (by 26-103%) for insulin- relative to vehicle-treated mice for alpha- and gamma-ENaC in the homogenate (H), and plasma membrane-enriched fraction (MF), with no difference in the vesicle-enriched fraction (VF). Similarly, beta-ENaC was significantly increased in MF (by 45%) but no change in the H. It was, however, significantly decreased in the VF (by 28%) with insulin. In agreement, immunoperoxidase labeling demonstrated relatively stronger apical, relative to cytosolic, localization of alpha-, beta-, and gamma-ENaC with insulin, whereas, with vehicle, labeling was fairly evenly dispersed throughout collecting duct principal cells. Furthermore, Western blotting showed insulin increased SGK-1 (by 75%) and phosphorylated-SGK band densities (by 30%) but only in the MF. These studies demonstrate novel in vivo regulation of renal ENaC activity and subunit proteins and SGK-1 by insulin in the acute time frame in the mouse.
Place, publisher, year, edition, pages
2007. Vol. 293, no 1, F178-F185 p.
epithelial sodium channel, SGK-1, hyperinsulinemia
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:uu:diva-104059DOI: 10.1152/ajprenal.00447.2006ISI: 000247850500025PubMedID: 17389677OAI: oai:DiVA.org:uu-104059DiVA: diva2:220125