Age-associated changes in content of cyclic adenosine-3', 5'-monophosphate (cAMP), cyclic guanosine-3',5'-monophosphate (cGMP) and in activity of phosphodiesterase-cAM (pDE-cAM) in spleen T-lymphocytes from C3HA mice.

The present work deals with the content of cyclic nucleotides and PDE activity in spleen T-lymphocytes of young and old animals. The cAMP/cGMP ratio is shown to increase with age chiefly owing to the reduction in cGMP level and in PDE activity which induces inhibition of proliferation and 3/1-thymidine incorporation in lymphocyte DNA in response to mitogens concanavalin A (Con A) and phytohemagglutinin (PHA). Isoproterenol, biogenic amines, theophylline, dibutyryl cAMP influence less effectively the level of cyclic nucleotides and PDE activity of T-lymphocytes from old animals than those from young mice. The data suggest that the change in the intracellular content of cyclic nucleotides leads to the reduction in proliferation and immunologic response to one or another antigen.