Effects of anchorage-modulating doses of concanavalin A, microtubule-disrupting drugs and microfilament perturbants, cytochalasins, on the phosphatidylinositol response of rat lymph-node cells.

In lymphocytes isolated from rat lymph nodes, concanavalin A stimulated the 32PO4 incorporation into phosphatidylinositol and phosphatidic acid in a dose-dependent manner up to 200 micrograms of the lectin per ml of the lymphocyte culture. [3H]Thymidine incorporation was found to be optimal at 2 micrograms concanavalin A per ml of the culture when the incorporation was examined at the same cell density as was used in the determination of the 32PO4 incorporation. As previously described (Wang, J.L. and Edelman, G.M. (1978) J. Biol. Chem. 253, 3000-3007), the [3H]thymidine incorporation was inhibited at doses higher than 5 micrograms/ml in a dose-dependent manner. These results indicate that concanavalin A produced the phosphatidylinositol PI response of rat lymph-node cells in the dose range in which the mobility and distribution of lymphocyte surface receptors were modulated by the lectin (Yahara, I. and Edelman, G.M. (1972) Proc. Natl. Acad. Sci. U.S.A. 69, 608--612). Colchicine and vinblastine at a concentration of 10(-4) M did not inhibit the concanavalin A-induced PI response of rat lymph-node cells. Cytochalasins B and D at a concentration of 10(-5) M enhanced the concanavalin A-induced PI response to some degree. All the results obtained suggest that submembranous assemblies of microtubules and microfilaments do not play an indispensable role in the sequence of events involved in the PI response of rat lymph-node cells.