Effect of catecholamines on lymphopoiesis in fetal mouse thymic explants

Fetal thymic explants (14 days of gestation) from Balb/c mice were grown in organ culture for up to 12 days and the pattern of lymphopoiesis was monitored by 125IUdR incorporation and cell yields of such lobes in the presence of adrenergic agents. It was observed that, after 3 days of cultures, phenylephrine stimulated lymphopoiesis in thymic explants, whereas some inhibition was observed with isoproterenol. These observations were confirmed by autoradiography. It was also observed that cells obtained from phenylephrine-treated cultures had greater mitogen reactivity than either control (untreated) or isoproterenol-treated cultures. The possible role of cyclic nucleotides as intracellular mediators of thymocyte maturation is discussed.