The Possible Mediation by Cyclic AMP of the Stimulation of Thymocyte Proliferation by Cyclic GMP

Very low (5 × 10-12 to 10-10M), as well as higher (10-6 to 5 × 10-6M) concentrations of cyclic guanosine 3', 5'-monophosphate (cyclic GMP) stimulate the proliferation of rat thymic lymphocytes in vitro, but intermediate concentrations (10-9 to 10-7M) of the cyclic nucleotide do not affect cell proliferation. Other guanosine monophosphates such as guanosine 5'-monophosphate (5'-GMP) and cyclic guanosine 2',3'-monophosphate (cyclic 2',3'-GMP) do not affect thymocyte proliferation.