The link between Rottlerin (Na+.K+)-ATPase activity and Na+-dependent glutamate transport.

NANITSOS EK, SHIN JW, NGUYEN KTD, ACOSTA GB, RAE C AND BALCAR VJ.

Innsbruck, Austria, 21-26 August 2005.

Congreso; 20 th Biennial Meeting of Internationl Society for Neurochemistry and the European Society for Neurochemistry.; 2005

ISN

A tight link has been suggested between the Na+,K´-ATPasc and Na-­dependent glutamate transpon (GluT) in brain tissue. This was tested lIsing ´prisms´ 01´ rat cerebral conex wherc Na".K+-ATPase activity Vas complete]y inhibited by ouabain (IC5o= 17/lM) as 1l1easured by Rb­uptake using alOmic absorplion spectroscopy. Digoxin (I00/lM) was found to have a similar effect. Ouabain also inhibiled [´H]-L-glutama[e uptake (IC50 < I uM) suggesting that GluT is indeed linked to a frac­tion of Na+/K´ dependent ATPase strongly inhibited by ouabain. In addition to the GluT substrales and inhibitors tested, none of the glu­tamate receptor agonisls and antagOnlSIS had any effect on Rb+ uptake with the exception 01´ (R,S)-(relrazol-5-yl)-glycine and N-methyi­D-aspartate callsing a de crease in Rb- lIptake. Transmission electron microscopy confirmed that the cortica! tissue re1l1aineel healthy af¡er being exposed to the mechanical srress causeel by the ´chopping´ process. Rottlerin, a specific inhibitor of pro te in kinase e-delta (PKC­o), inhibited Na+,K+-ATPase activity in cultured astrocytes whibr increasing oxygen consumption. The e1isrribution of glutamate transporter GLAST between the cytoplasm and cell membranes of cultured astrocytes was altered by D-aspartate but then inhibited by rottlerin. However, since the redistribution of GLAST towards the membrane depends on the activity of GluT, it seems that the rottlerin effect on metabolism and the conseguent decrease in the availability of ATP can provide an adeguate alternative explanation without involving PKC-delta in the process.