Effects of the peptide toxin from XXXX on intracellular calcium, pH and membrane integrity in @entity1 cells.

@entity1 @entity137 @entity19 @entity16589 @entity3460 @entity141
Extracts of water blooms of the toxic cyanobacterium @entity16589 showed a range of @entity137 not related to their ability to lyse @entity1 red cells. The HPLC-purified heptapeptide toxin (mol. wt. 1035) from @entity16589 did not lyse red cells at up to 500-fold higher concentrations than that required to kill @entity19 . This toxin (LD50 110 micrograms/kg for male @entity19 ) was used to investigate in vitro effects on isolated thymocytes, hepatocytes, mammary alveolar cells, and cultured Swiss 3T3 fibroblasts. Thymocytes were stimulated to progressive @entity141 entry by toxin (0.1-10 micrograms/ml), reaching a peak after approx. 5 min. No deformation, intracellular pH change, @entity3460 entry or cell lysis was seen within 60 min at 37 degrees C. Hepatocytes were grossly deformed by the toxin, with a dose/response relationship between 0.1 and 1.0 microgram/ml. No progressive @entity141 entry was observed on toxin addition, instead a rapid rise in intracellular @entity141 , presumably from intracellular sources. No change in intracellular pH, @entity3460 exclusion or cell lysis was observed over 60 min. Mammary alveolar cells and 3T3 fibroblasts were unresponsive to toxin at the concentrations tested. No change in protein synthesis or nucleic acid synthesis in thymocytes was observed after culture with 0.5 or 5.0 micrograms/ml toxin. It was concluded that cytoskeletal changes in deformed hepatocytes (the target cells in vivo) demonstrated the most probable cellular basis for @entity137 , rather than changes in membrane permeability or cell metabolism.
