I 131 and P 32 Accumulation in Anuran Thyroid Gland in Normal and Accelerated Metamorphosis. ∗

Abstract

Summary and conclusions

1) The uptake of I¹³¹ and P³²- by the developing thyroid of Rana tadpoles has been determined in normal and accelerated metamorphosis. Radioactive measurements of the isolated gland (estimated weight, 50-200 μg) disclose a progressive increase in radioiodine accumulation throughout normal development. The effect is not paralleled with radiophosphorus although significantly increased P³² thyroidal uptakes eventually occur in advanced development. Exogenous thyrotrophin augments I¹³¹ and P³² accumulation in the thyroids of young tadpoles. The applicability of the thyroidal response to the bioassay of thyrotrophin is discussed. 2) The enhancement of iodine and phosphorus uptake by the larval thyroid is considered to reflect increased tempo of thyroid function in amphibian development. The fundamental role of pituitary-thyroid interaction in anuran metamorphosis is reemphasized.