Thyroidal Iodine Metabolism in Inbred and F1 Hybrid Mice

Abstract

Thyroidal iodine metabolism was studied in four inbred strains of mice and two groups of F1 hybrids by use of radioiodine. Significant strain differences were found in both the 48-hour thyroidal retention of I131 and its output rate constant. Three closely related groups studied were C57BL/6, C57BR/cd and BBF1, their F1 hybrid. The other three groups included A/Jax, BALB/c and CAF1, their F1 hybrid. C57BL/6 mice had a significantly faster output rate and lower 48-hour I131 retention than any other group. The first three groups listed had a more rapid output rate and lower 48-hour retention than the last three. In intergroup comparisons and inverse relationship between I131 output rate and 48-hour retention was clearly shown. The results indicate that in mice pituitary TSH output, as indicated by thyroidal I131 output rate and thyroidal iodine pool size, is controlled by separate genetic factors.