title: Amiloride-sensitive Na+-H+ exchange in platelets and leukocytes: detection by electronic cell sizing.
abstract: A new method was developed to detect the activity of the Na+-H+ exchange system as changes in cell volume. The cytoplasmic pH of isolated cells in suspension was lowered by incubation in Na-propionate medium, due to permeation of the protonated acid. This resulted in activation of Na+-H+ countertransport, measurable either as a Na+-dependent alkalinization or as an increase in 22Na+ uptake, both of which are amiloride sensitive. The continued operation of the antiport on prolonged exposure to Na-propionate results in a considerable increase in Na+ (and presumably propionate-) content. This is accompanied by an osmotic water shift and cell swelling, detectable by electronic sizing. This method was used to investigate the presence of the Na+-H+ exchanger in human platelets, neutrophils, lymphocytes, and monocytes as well as in cultured cell lines of B and T lymphoblasts and of macrophages. All these cell types displayed an amiloride-sensitive swelling when suspended in Na-propionate media. The results suggest the ubiquity of the Na+-H+ exchange system in the plasma membrane of nucleated mammalian blood cells.
mesh_terms: D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D001792:Blood Platelets / Q000378:metabolism*; D002452:Cell Count; D003470:Culture Media; D003593:Cytoplasm / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D007962:Leukocytes / Q000378:metabolism*; D008214:Lymphocytes / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism; D009504:Neutrophils / Q000378:metabolism; D009995:Osmosis; D011422:Propionates / Q000494:pharmacology; D011719:Pyrazines / Q000494:pharmacology*; D051381:Rats; D012964:Sodium / Q000378:metabolism*
chemical_list: D003470:Culture Media; D007473:Ion Channels; D011422:Propionates; D011719:Pyrazines; D000584:Amiloride; D012964:Sodium