Thymidine and Testosterone Incorporation by Bursal and Thymic Lymphocytes

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Abstract
After 12 days of incubation tritiated thymidine (3HTdR) was injected into the allantoic cavity or applied to the air cell of fertile eggs. At varying time periods after 3HTdR administration the bursa of Fabricius, thymus, and spleen were removed from the chick embryo and the amount of 3HTdR was assayed by liquid scintillation. The highest concentration of 3HTdR was observed two days after applying the isotope to the air cell with the greatest concentration of 3HTdR being in the spleen, then the bursa, and finally the thymus. The in vitro exposure of bursal and thymic cells to 3HTdR or to tritiated testosterone (3HTestR) revealed significantly more uptake of both isotopes by bursal than thymic cells. These data establish an optimum route and sampling period for in vitro 3HTdR studies with embryos and suggest that bursal cells are more receptive than thymic cells to both 3HTdR and 3HTestR. The latter may, in part, explain why cold testosterone administered to chicken embryos will eliminate bursal cells with attendant immunological consequences and have little or no effect on thymic cells.