In vitro thymidine uptake and incorporation into thymic and bursal lymphocytes from young hypothyroidic chickens

Experiments were conducted to evaluate the ability of thymic and bursal lymphocytes from hypothyroidic chicks to take up 3H-thymidine. To produce hypothyroidism, chicks were fed a diet containing thiouracil (0.1%) from day of hatch to 3 weeks of age. At 1, 2 and 3 weeks of age, body weights were significantly lower for hypothyroid chicks, and at 2 and 3 weeks of age, the relative weights of the thymus and bursa were significantly less than those of controls. Furthermore, chicks treated with thiouracil had significantly lower serum concentrations of 3,5,3'-triiodothyronine (T3) and thyroxine (T4). Thymic cells from hypothyroid chicks incorporated less 3H-thymidine at 1 and 3 weeks of age as assessed by liquid scintillation counting and autoradiography. Liquid scintillation counts for labeled bursal cells from hypothyroid chicks were not lower at 1 week of age, but the counts were lower at 3 weeks of age. Autoradiographic studies with bursal cells revealed that 3H-thymidine incorporation was less, but not significantly less, in medium-size lymphocytes from thiouracil-treated chicks at both 1 and 3 weeks of age. Thymidine incorporation into large bursal cells was affected more by thiouracil treatment at 1 than 3 weeks of age.