Factors Contributing to the Difference in Propylthiouracil Goitrogenesis in Rats and Guinea Pigs

Abstract

Summary and Conclusions

(1) The difference between the rat and guinea pig with respect to thiouracil goitrogenesis was investigated using the binding of I¹³¹ to surviving thyroid slices as a measure of thyroid hormone production. (2) Propylthiouracil in concentrations ranging from 10^-7 M through 10^-5 M inhibited hormone synthesis to an equal extent in both rat and guinea pig thyroid slices. In vivo studies have indicated the compound to concentrate in the gland to a comparable degree in both species. On the other hand, in the absence of propylthiouracil, hormone synthesis in rat thyroid slices occurred at 5 times the rate for guinea pig thyroid slices. (3) In view of these observations it is suggested that the species difference in thiouracil goitrogenesis can be accounted for by differences in the rates of peripheral utilization of circulating thyroid hormone.