[Effect of thymalin on the cyclic nucleotide system in the mouse spleen]

The effect of the thymus preparation thymalin (1000 micrograms/mouse, i.p.) on the system of cyclic nucleotides in the spleen has been studied. The preparation produced two-phasic changes in the content of cAMP and cGMP, as well as in the activity of cAMP phosphodiesterase. The changes in the spleen cAMP content are consequent on those in the activity of phosphodiesterase.