Long-term regulation of Na+,K+-ATPase in opossum kidney cells by ouabain

✍ Scribed by E. Silva; P. Soares-da-Silva

• Publisher: John Wiley and Sons
• Year: 2011
• Tongue: English
• Weight: 619 KB
• Volume: 226
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.22575

✦ Synopsis

Abstract

Na^+^,K^+^‐ATPase, a basolateral transporter responsible for tubular reabsorption of Na^+^ and for providing the driving force for vectorial transport of various solutes and ions, can also act as a signal transducer in response to the interaction with steroid hormones. At nanomolar concentrations ouabain binding to Na^+^,K^+^‐ATPase activates a signaling cascade that ultimately regulates several membrane transporters including Na^+^,K^+^‐ATPase. The present study evaluated the long‐term effect of ouabain on Na^+^,K^+^‐ATPase activity (Na^+^ transepithelial flux) and expression in opossum kidney (OK) cells with low (40) and high (80) number of passages in culture, which are known to overexpress Na^+^,K^+^‐ATPase (Silva et al., 2006, J Membr Biol 212, 163–175). Activation of a signal cascade was evaluated by quantification of ERK1/2 phosphorylation by Western blot. Na^+^,K^+^‐ATPase activity was determined by electrophysiological techniques and expression by Western blot. Incubation of cells with ouabain induced activation of ERK1/2. Long‐term incubation with ouabain induced an increase in Na^+^ transepithelial flux and Na^+^,K^+^‐ATPase expression only in OK cells with 80 passages in culture. This increase was prevented by incubation with inhibitors of MEK1/2 and PI‐3K. In conclusion, ouabain‐activated signaling cascade mediated by both MEK1/2 and PI‐3K is responsible for long‐term regulation of Na^+^ transepithelial flux in epithelial renal cells. OK cell line with high number of passages is suggested to constitute a particular useful model for the understanding of ouabain‐mediated regulation of Na^+^ transport. J. Cell. Physiol. 226: 2391–2397, 2011. © 2010 Wiley‐Liss, Inc.