Effects of carrageenan-a macrophage toxic agent-on antibody synthesis and on delayed hypersensitivity in the guinea pig

Carrageenin-induced thrombosis in rats and mice: a model for testing antithrombotic substances?

Among different carrageenins, kappa-carrageenans were found to be thrombogenic, whereas lambda-carrageenins were inactive in this respect, although the latter substances exerted a stronger edemogenic activity. Kappa-carrageenin (Sigma) was the most potent thrombogen. As the consequence of thrombosis tail infarction became visible some minutes after i.v. administration, but it was delayed for about 3 hours after the i.p. route and for about 6 hours after subplantar injection. Infarction frequency as well as extent of infarction was inhibited by heparin, cyproheptadine, phentolamine and dibenamine. Other substances like aspirin and dipyridamole showed no or only weak effects. Advantages of the carrageenin-induced thrombosis model in rats and mice are: (i) simple induction in small laboratory animals, (ii) easy observation and quantification all the time without killing the animals, and (iii) possible external testing of antithrombotic agents by applying substances on the tail.

Carrageenan-mediated suppression or augmentation of mitogen-induced lymphocyte proliferation

The effects of carrageenan on mitogen-induced lymphocyte proliferation were studied in the guinea pig. According to the dose used, carrageenan displayed opposite effects on thymidine uptake by spleen cells or peripheral blood leukocytes stimulated by Concanavalin A or phytohemagglutinin (25 micrograms ml-1 carrageenan increased whereas 0.25 microgram ml-1 depressed thymidine incorporation). Carrageenan, at the high concentration which increased thymidine uptake by mitogen-stimulated spleen cells, potentiated the enhancing activity of macrophages that was observed with cell suspensions containing 20% macrophages. Conversely, low concentrations of carrageenan abolished the enhancing effect of macrophages. These effects of carrageenan on lymphocyte proliferation could be explained by its activities on a macrophage functional subset rather than on the whole macrophage population.