INCREASE OF CYCLIC-GMP INDUCED IN MURINE THYMOCYTES BY THYMOSIN FRACTION-5

Using a radioimmunoassay (RIA) for the determination of cyclic[c]AMP and an acetylation-RIA procedure to measure cGMP, cGMP levels, but not cAMP levels, were significantly elevated in murine thymocytes which had been incubated with preparations containing the thymic hormone, thymosin. Stimulation of intracellular cGMP levels was seen as early as 1 min after incubation with thymosin fraction 5 and was maximal at approximately 10 min. Dose response studies indicated an optimum stimulation of cGMP with a thymosin concentration of 100 .mu.g/ml. A control spleen fraction prepared by an identical procedure as fraction 5 did not affect the levels of either cyclic nucleotide.