Electrical properties of thyroid follicles in normal and thyrotropin-injected frogs and in premetamorphic and metamorphic tadpoles

Abstract

Using glass capillary microelectrodes inserted into individual thyroid follicles, measurements were made of potential difference and electrical resistance across the epithelial wall in the frog Rana pipiens. Measurements were made in thyroids of tadpoles from stage IV through metamorphosis and in adult thyroids from untreated frogs and those injected with thyroid-stimulating hormone (TSH). TSH lowered both potential and resistance. Gradual lowering in potential and resistance in thyroid follicles was found in tadpoles between stages IV and XVI. After this, and through metamorphic climax, follicular potential and resistance increased again to early premetamorphic levels. These changes were closely and inversely related to thyroid functional state. It was concluded that electrical properties provide a sensitive index to functional state in individual thyroid follicles.