Examination of Erythrocyte I 131 -T 4 and I 131 -T 3 Uptake Test for Thyroid Function in Chickens. ∗

Abstract

Summary and discussion

From the results of this work the in vitro erythrocyte I¹³¹-T₃ uptake test was not useful for the measurement on thyroid function in chickens.

Sodee(2) and Szabo(4) pointed out that the outcome of the test was dependent upon avoiding technical variations in the procedure. In the present investigation, temperature was controlled and the same treatment was given to all samples. According to Saxena et al(3), the use of propylthiouracil did not appear to alter the erythrocyte's ability to take up I¹³¹-T₃; therefore, the use of propylthiouracil to produce hypothyroidism should not have affected the outcome of the test. It is possible that there were no differences in thyroid secretory rate among the 3 groups of chickens, since no parameters of thyroid function (PBI, I¹³¹ uptake or I¹³¹ release) were measured. However, since thyroid weights in mg% were significantly different among the 3 groups and the body weights in the propylthiouracil group were significantly low, it is improbable that thyroid function in all 3 groups was the same.

Another contributing factor or factors in the failure of this test may have been the low PBI value reported in avian plasma by Mellen and Hardy(5). Tata and Shellabarger (6,7) also have reported that T₄ and T₃ are not transported in avian sera by the alpha-type globulin found in mammals, but are bound less firmly to the serum albumin fraction. Since in mammals this test actually measures the degree of saturation of several plasma proteins, particularly the globulin fraction with T₃, it is conceivable that in chickens T₃ not bound to plasma proteins would become bound to a greater degree on the erythrocytes. The latter possibility was observed earlier by Heninger and Newcomer (8).