Heterogeneous pathways of Ca2+ metabolism in the triggering of the proliferative process in rat thymocytes

Concanavalin A induces in rat thymocytes a calcium uptake at 1 h exposure and proliferative response after 24 h exposure. Phosphodiesterase activity parallels the proliferative response (thymidine uptake). Valinomycin, monensin and a small dose of ouabain also induce calcium uptake, but do not lead to thymidine uptake later. The latter treatments reduce, in some instances drastically, the concanavalin A response with respect to thymidine uptake. Trifluoperazine reduces the unstimulated thymidine uptake and the concanavalin A induced thymidine uptake. These results suggest that calcium has a decisive role in inducing proliferation but that some ways of increasing cellular Ca²⁺ concentration interfere in other steps with the DNA synthesis.