Calcium-Mediated Effects of Cyclic GMP on the Stimulation of Thymocyte Proliferation by Prostaglandin E 1 1

Abstract

Summary

Low (10^-11 to 10^-10 M) and high (10^-6 to 5 × 10^-6 M) cyclic GMP concentrations raise the cellular cyclic AMP content and stimulate rat thymocyte proliferation, but intermediate (10^-9 to 10^-7 M) cyclic GMP concentrations have no effect on these activities. The intermediate cyclic GMP concentrations also do not affect the ability of prostaglandin E₁ (PGE₁) to raise the cellular cyclic AMP concentration and stimulate DNA synthesis. However, depending on the intracellular cyclic AMP content and the extracellular calcium concentration, the intermediate cyclic GMP concentrations can either strongly promote or completely inhibit progression of the PGE₁-stimulated, DNA-synthesizing cells into mitosis. It is concluded that calcium mediates the actions of cyclic GMP and an attempt is made to explain the complex actions of these agents on the mitogenic process.