ABSTRACT
Isolated rat enterocytes were incubated with E. coli heat-stable enterotoxin or buffer alone and the protein kinase activity and cyclic GMP level determined on the particulate fraction or cytosol, respectively. In the control cells, particulate protein kinase activity and cyclic GMP concentration were at a maximum after 20 sec and 1 min of incubation, respectively. In heat-stable enterotoxin-treated cells the particulate protein kinase activity was significantly increased (P less than 0.05) after 20 sec of incubation, but decreased (P less than 0.05) after 30 sec, 1 min and 2 min, when compared to the control reaction. During this time period the concentration of intracellular cyclic GMP increased 10-fold. The effect of heat-stable enterotoxin on particulate protein kinase activity and cyclic GMP concentration was dose-dependent. Analysis of radioactive membrane phosphorylation products indicate a role for phosphoproteins with a mol. wt of 25,000 and 120,000. These results suggest that the action of heat-stable enterotoxin may involve an effect on protein kinase.
Subject(s)
Enterotoxins/pharmacology , Escherichia coli , Protein Kinases/metabolism , Animals , Calmodulin/metabolism , Cell Membrane/metabolism , Cyclic AMP/metabolism , Cyclic GMP/metabolism , Dose-Response Relationship, Drug , Drug Stability , Electrophoresis, Polyacrylamide Gel , Hot Temperature , Intestines/cytology , Intestines/enzymology , Intestines/ultrastructure , Intracellular Fluid/metabolism , Membrane Proteins/metabolism , Mice , Phosphorylation , RatsABSTRACT
Splenic lymphocytes from preleukemic AKR mice are capable of participating in various cell-mediated immune responses. Spleen cells from AKR mice aged 1 to 10 months produced a significant graft-versus-host reaction when injected into 8-day-old AKR x C57Bl/6 F(1) hybrids. Splenic lymphocytes from similarly aged mice were also capable of responding to allogenic stimulation in a mixed lymphocyte reaction. AKR mice aged 1 to 10 months developed a contact sensitivity response to picryl chloride. It was concluded that mice of this high-leukemic strain have a competent cell-mediated immune system and there is no depression of immunity during the preleukemic period.
