A COMPARISON OF THE RESPONSES OF TRITURUS AND DESMOGNATHUS TO THYROID-STIMULATING HORMONE ADMINISTRATION

¹ Biology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, Department of Biology, Catholic University of America, Washington 17, D. C., and University of Virginia, Charlottesville, Virginia

1. Specimens of Triturus viridescens and Desmognathus fuscus were given injections of Armour's Thytropar on alternate days.

2. Histological examination of the thyroid glands of experimental and control animals showed that both species gave maximal response after only four injections, the follicular epithelium being greatly heightened and intrafollicular colloid almost completely discharged, and that thé response persisted for 3-4 days after cessation of treatment, but then declined and disappeared by 7 days.

3. Measurements of uptake and turnover of I¹³¹ by the thyroids of animals given six injections of thyrotropin showed a high uptake and a rapid turnover in Desmognathus. In Triturus the effect of the treatment upon I¹³¹ uptake was also marked and the radioiodine was retained at a high level throughout the counting period (60 hours).

4. It is concluded that the Triturus thyroid is more responsive to exogenous TSH than is that of Desmognathus, and that this is related to an exceptionally low TSH content and production in the anterior pituitary of Triturus.