Na+/H+ exchange: What, where and why?

Hepatocellular Na+/H+ exchange is activated early, transiently and at a posttranscriptional level during rat liver regeneration

“…pling growth factor-induced activation of Na' /H + exchange with cell proliferation (1,2). Moreover, growth factor-mediated phosphorylation events in uiuo are likely in equilibrium with dephosphorylation reactions (46).…”

“…Under the conditions used, mRNA extracted from whole liver therefore largely represents hepatocellular mRNA. For Northern-blot analysis, polyadenylate RNA was electrophoresed on a 1.2% agarose gel containing 6.6% formaldehyde (271, transferred to a nylon membrane (ZetaProbeR; BioRad, Richmond, VA) and probed with DNA probes specific for: (1) the growth factor-inducible Na+/H+ antiport of rat kidney (kind gift of Dr. R. Krapf) (5, 28) and (2) (30). The filters were washed twice and for 30 min each with 2 x standard saline citrate (150 mmol/L NaCl, 15 mmol/L sodium citrate, pH 7.0) at 42" C, 2 x standard saline citrate/l%SDS at 65" C and 0.1 x standard saline citrate at room temperature (31) and exposed to x-ray film (Kodak X-OMATR; Eastman Kodak Co., Rochester, NY) with intensifying screen.…”

“…changer by growth factors is mediated by an increase of the antiporter's affinity for intracellular H + (1)(2)(3), is most likely caused by growth factorinduced antiport phosphorylation (4) and leads to increases in intracellular pH (pHi) or Na+ concentration, which are thought to play a permissive role, at least, during mitogenesis (1)(2)(3). Na+/H+ exchange is also known to be regulated at a transcriptional level.…”

Hepatocellular defence against acidosis is preserved after cold storage

“…1A). As starting pH i , which is known to affect Na þ /H þ antiport activity [19,20,29,30,36,37], was similar under all conditions (Table 2), it seems legitimate to directly compare these initial dpH i /dt. The initial rate of this pH i recovery (dpH i /dt) did not significantly differ in freshly isolated (n ¼ 8 determinations in five cell preparations), 24-h (n ¼ 5 determinations in the same five cell preparations) and 48-h (n ¼ 7 determinations in the same five cell preparations) UW-stored cells ( Table 1).…”

“…The initial rate of this pH i recovery (dpH i /dt) did not significantly differ in freshly isolated (n ¼ 8 determinations in five cell preparations), 24-h (n ¼ 5 determinations in the same five cell preparations) and 48-h (n ¼ 7 determinations in the same five cell preparations) UW-stored cells ( Table 1). As starting pH i , which is known to affect Na þ /H þ antiport activity [19,20,29,30,36,37], was similar under all conditions (Table 2), it seems legitimate to directly compare these initial dpH i /dt. Initial rates of pH i recovery from an intracellular acid load reflect, however, transport activity of Na þ /H þ antiport only if intracellular buffering capacity (b t ) is not altered by UW preservation.…”