title: Relationship of free intracellular calcium to the cytolytic activity of Entamoeba histolytica.
abstract: Entamoeba histolytica adherence and destruction of host cells is required for in vivo pathogenicity; amebic in vitro adherence is mediated by a galactose- or N-acetyl-D-galactosamine-inhibitable surface lectin (Gal/GalNAc adherence lectin). Free intracellular Ca2+ concentration [( Ca2+]i) was measured in living amebae and target cells during amebic cytolysis of Chinese hamster ovary (CHO) cells and human polymorphonuclear neutrophils by utilizing the Ca2+ probe Fura-2 and computer-enhanced digitized microscopy. Motile E. histolytica trophozoites had oscillatory increases in [Ca2+]i in head or tail regions; however, there was no increase in regional or total amebic [Ca2+]i upon contact with a target CHO cell. Target CHO cells and polymorphonuclear neutrophils demonstrated marked irreversible increases in [Ca2+]i within 30 to 300 s following contact by an ameba (P less than 0.01); increased [Ca2+]i preceded the occurrence of nonspecific surface membrane permeability and death of the target cell. Target CHO cells contiguous on a monolayer to a cell contacted by an ameba experienced a rapid but reversible rise in [Ca2+]i (P less than 0.01) and were not killed. Galactose (40 mg/ml) totally abrogated the rise in target CHO cell [Ca2+]i that followed contact by amebae (P less than 0.01); immunoaffinity-purified amebic Gal/GalNAc adherence lectin (0.25 micrograms/ml) induced a rapid and reversible rise in CHO cell [Ca2+]i (P less than 0.01) which was inhibited by galactose. Amebic [Ca2+]i was not elevated following parasite adherence to target cells; a rapid and substantial rise in target cell [Ca2+]i occurred which was mediated, at least in part, by the Gal/GalNAc adherence lectin of the parasite and led to the death of target cells.
mesh_terms: D000268:Adhesiveness; D000818:Animals; D001826:Body Fluids / Q000502:physiology*; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002460:Cell Line; D002465:Cell Movement; D002470:Cell Survival / Q000187:drug effects; D006224:Cricetinae; D003412:Cricetulus; D004748:Entamoeba histolytica / Q000378:metabolism / Q000472:pathogenicity* / Q000502:physiology; D005260:Female; D005690:Galactose / Q000494:pharmacology; D007424:Intracellular Fluid / Q000187:drug effects / Q000502:physiology*; D037102:Lectins / Q000494:pharmacology; D009504:Neutrophils / Q000469:parasitology; D010053:Ovary
chemical_list: D037102:Lectins; D002118:Calcium; D005690:Galactose