Nongenomic Effects of Aldosterone on Renal Protein Expressions of pEGFR and pERK1/2 in Rat Kidney

Abstract

Background: In vitro studies have demonstrated that aldosterone elicits nongenomic actions by enhancing protein expressions of phosphorylated epidermal growth factor receptor (pEGFR) and phosphorylated extracellular signal-regulated kinases 1/2 (pERK1/2). There are no available in vivo investigations regarding this action of aldosterone on renal pEGFR-pERK1/2 protein expressions. Methods: Male Wistar rats received normal saline solution, low-dose (LA: 150 µg/kg BW) or high-dose aldosterone (HA: 500 µg/kg BW) by intraperitoneal injection. After 30 min, protein abundances and localizations of renal pEGFR and pERK1/2 were determined by Western blot and immunohistochemistry. Results: Plasma aldosterone levels were increased in LA and HA groups (p < 0.001). Aldosterone enhanced renal pEGFR and pERK1/2 protein abundances (p < 0.001). HA showed a greater stimulation on pEGFR immunoreactivity than LA in the glomerulus, vasa recta, and thin limb of Henle’s loop in the inner medulla area. LA provided more reactivity of pERK1/2 in the thick ascending limb of Henle’s loop, outer medullary collecting duct, and proximal straight tubule, whereas HA illustrated more pERK1/2 activation in the glomerulus, peritubular capillary, and inner medulla region. Conclusion: This is the first in vivo study which demonstrates that aldosterone, via the nongenomic pathway, could elevate pEGFR and pERK1/2 protein abundances and expressions in the rat kidney. These results indicate that aldosterone induces phosphorylation of EGFR upstream of ERK1/2.

Rapid Nongenomic Action of Aldosterone on Protein Expressions of Hsp90(αandβ) and pc-Src in Rat Kidney

“…All animal protocols were approved by the Ethics Committee of Research, Chulalongkorn University. Serum creatinine of each rat should be <1 mg/dL [5]. The rats were divided into two groups ( n = 8/group): sham (normal saline solution; NSS: 0.5 mL/kg BW by intraperitoneal injection, i.p.…”

“…Kidneys were removed, and a half of each kidney was fixed in liquid nitrogen and then stored at −80°C until use for measurement of Hsp90 α , Hsp90 β , and pc-Src protein abundances by Western blot analysis. The other half of renal tissue was fixed in 10% paraformaldehyde for localization of these proteins by immunohistochemistry [5]. …”

“…The measurement of protein abundance was performed as previously described [5, 11]. Proteins were resolved on 10% sodium dodecyl sulfate polyacrylamide gel eletrophoresis (SDS-PAGE) for Hsp90 α , Hsp90 β , or pc-Src and blotted onto nitrocellulose membrane (Bio-Rad, Hercules, CA, USA).…”

“…Detection of protein localization was performed as previously described [5]. Paraffin-embedded kidney sections were cut at 4  μ m in thickness.…”

“…A recent in vivo study was conducted in our laboratory. It was the first to demonstrate that aldosterone, via nongenomic pathway, elevated phosphorylated EGFR (pEGFR) and pERK1/2 protein abundances and expressions in rat kidney [5]. …”