ABSTRACT
The presence of an antiport that exchanges outside sodium for intracellular hydrogen has been demonstrated in several cell types including neutrophils and platelets. 1 – 21 This exchanger is a ubiquitous transport system with a tightly coupled 1:1 stoichiometry, and it has affinity for Li+ and N H 4 + https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781351074889/d386649a-919c-4672-a203-15fea85f494f/content/eq225.tif"/> in addition to Na+ and H+. The importance of such a regulatory mechanism in relation to maintaining ionic and pH equilibrium during normal cellular metabolism is obvious. In addition, the importance of changes in intracellular pH in cell function or as a signal in the activation and/or regulation of cell activation is becoming increasingly apparent. It is entirely likely that changes in intracellular pH may be one of the early biochemical responses following cell stimulation. This hypothesis is based on the fact that there are large numbers of enzymes whose activities are pH dependent. Furthermore, the contractile activity of purified preparations of actin and myosin and microtubule assembly and disassembly have also been shown to be dramatically influenced by relatively small changes in pH. 22 – 23 Changes in intracellular pH have been found to play a role in sea urchin egg fertilization, cell growth and division, mechanical properties in muscle, and possibly in pancreatic cell function and platelet and neutrophil activation. 23 – 30
