CRITICAL STUDIES ON THE DETERMINATION OF THE THYROID SECRETION RATE IN COLD-ADAPTED ANIMALS,
Abstract
There is ample evidence in the literature showing that cold adaptation in mammals can be accompanied by increased as well as by decreased thyroid activity. Measurement of thyroid secretion rate by determining the amount of L-thyroxine required to bloc the thyroidal I131 release, according to Perry's method, revealed that the thyroxine requirement of 6 degrees C-acclimated rats was twice as high as that of controls (5.5 = 0.7 micrograms/100g/day against 2.73 = 0.3 micrograms /100g/day for the controls). The requirement of the white rats acclimatized to cold outdoors during the winter on the other hand, was less than in the controls (1.8 micrograms/100g/day). The larger amount of thyroxine found in the feces of the 6 degrees C-acclimated rats (5.75 = 0.3 micrograms/day as compared to 2.84 = 0.4 micrograms/ day for the controls), the similar rate of urinary elimination of I131 in both groups, and the greater fecal elimination of the same isotope in the 6 degrees C-rats indicates that the greater requirement for thyroxine in these animals is at least partly due to increased fecal loss of the hormone. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 26, 1963
- Accession Number
- AD0424523
Entities
People
- O. Heroux
- R. W. Brauer
Organizations
- Naval Radiological Defense Laboratory