Somchit Eiam-Ong, Kittisak Sinphitukkul, Krissanapong Manotham and Somchai Eiam-Ong
Previous in vitro studies showed that aldosterone rapidly stimulates protein kinase C alpha (PKC α) that could activate alpha (α) 1 isoform of Na, K-ATPase and then enhances its activity. There are, however, no in vivo data that demonstrate the rapid effects of aldosterone on renal protein expressions of PKC α and α1-Na, K-ATPase simultaneously. The present study further investigates the expression of these proteins. Male Wistar rats were intraperitoneally injected with normal saline solution or aldosterone (150 μg/kg BW). After 30 minutes, abundances and localizations of PKC α and α1-Na, K-ATPase proteins were determined by Western blot analysis and immunohistochemistry, respectively. Aldosterone administration significantly increased plasma aldosterone levels from 1,251.95 ± 13.83 to 6,521.78 ± 209.92 pmol/L. By Western blot analysis, aldosterone enhanced renal protein abundances of PKC α (homogenate samples) and α1-Na, K-ATPase (plasma membrane) approximately 50% and 30%, respectively (P<0.05). From immunohistochemistry examination in sham group, the protein expression of PKC α was prominent in the medulla. Aldosterone stimulated the expression both in the cortex and medulla with the translocation from the basolateral to luminal side of the proximal convoluted tubule (PCT). As for α1-Na, K-ATPase protein expression, the sham rats showed a strong immunostaining in the distal convoluted tubules, collecting ducts, and thick ascending limbs. Aldosterone elevated the expression in the PCT and medullary collecting duct (MCD). This in vivo study is the first to demonstrate simultaneously that aldosterone rapidly elevates PKC α and α1-Na, K-ATPase protein abundances in rat kidney. Both immunoreactivities were stimulated in the cortex and medulla. The greater affected areas were noted for PKC α expression, whereas the alterations of α1-Na, K-ATPase were observed only in the PT and MCD. The stimulation of Na, K-ATPase protein expression by aldosterone, per se, may occur through PKC activation.