title: Amiloride inhibition of DNA synthesis and immunoglobulin production by activated human peripheral blood mononuclear cells is independent of sodium/hydrogen antiport.
abstract: Activation of sodium/proton (Na+/H+) antiport activity has been shown to occur as an early event in mitogenesis. Because amiloride inhibits Na+/H+ antiport activity, it is hypothesized that mitogenesis may be inhibited by amiloride. In this work, we examined the effect of amiloride on DNA synthesis as measured by [3H]thymidine uptake and immunoglobulin (Ig) production as measured by an ELISA system in human peripheral blood mononuclear cells (PBM). Amiloride at 100 microM concentration inhibited irradiated Raji cell (*R)-activated and phytohemagglutinin-P (PHA-P)-stimulated DNA synthesis by 50 +/- 11% and 72 +/- 12%, respectively. IgG production was inhibited by 71% at 100 microM amiloride concentration in *R-activated PBM. This concentration of amiloride inhibited Na+/H+ antiport activity by 92%. Because amiloride is known to inhibit other pre-replicative cellular functions such as protein synthesis, we used an amiloride analogue, dimethylamiloride, which inhibited Na+/H+ antiport activity by 90% at a concentration of 1 microM without inhibition of PBM Ig or DNA synthesis. Furthermore, neither PHA-P nor *R-stimulated PBM demonstrated an intracellular alkalinization even after 6 hr of stimulation. Similarly, T cell-enriched or B cell-enriched populations did not show intracellular alkalinization after PHA-P or *R activation. Thus, it appears that Na+/H+ antiport activation is not an early event in PBM mitogenesis. The inhibition of mitogenesis by amiloride may be due to abrogation of premitotic events such as protein synthesis.
mesh_terms: D000328:Adult; D000584:Amiloride / Q000494:pharmacology*; D017920:Antiporters; D002352:Carrier Proteins / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis*; D006801:Humans; D007136:Immunoglobulins / Q000096:biosynthesis*; D007166:Immunosuppressive Agents / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects*; D011043:Pokeweed Mitogens / Q000494:pharmacology; D011522:Protons; D012964:Sodium / Q000378:metabolism
chemical_list: D017920:Antiporters; D002352:Carrier Proteins; D007136:Immunoglobulins; D007166:Immunosuppressive Agents; D011043:Pokeweed Mitogens; D011522:Protons; D000584:Amiloride; D004247:DNA; D012964:Sodium