THYROGLOBULIN IMMUNITY

Abstract

ABSTRACT Metamorphosis of Rana catesbeiana tadpoles immersed in a medium containing thyroxine (T4) occurred in 58 days, whereas 79 days were required for tadpoles treated with albumin + T4 complex in media, and at 121 days 50 % metamorphosis occurred in the group whose medium contained normal rabbit serum + T4. No metamorphosis occurred in tadpoles which had rabbit antiporcine thyroglobulin + T4 complex in media. Similarly the retardation of hind limb growth in comparison to the control at 58 days was most severe in animals treated with antithyroglobulin + T4 complex in media (74.3 % depression) followed by normal serum + T4 (60.1 % less) and bovine albumin + T4 complex (30 % inhibition) treated animals. In further investigations, in comparison to controls (only 125I-T4 in media), 62.4%, 77.0%, and 82.4% less 125I-T4 concentration was seen in viscera, tail, and carcass respectively of tadpoles treated with immune globulin + 125I-T4 in the media, whereas no change was seen in the group treated with normal gammaglobulin + 125I-T4 complex; similarly no changes in visceral 125I-T4 concentration were noted in groups whose media contained thyroglobulin in complex with 125I-T4. Present investigations therefore show that normal rabbit serum (apparently any good T4 binding protein) is a potent inhibitor of metamorphosis of tadpoles, the effectiveness mediated at least in part, on the inability of the larva to split thyroxine-protein complexes in their body. Antiporcine thyroglobulin rabbit serum was shown to be superior to normal rabbit serum in inhibiting tadpole metamorphosis, evidently due to additional T4 binding sites provided by the immune globulin. Available evidence indicates that antithyroglobulin binding of T4 is distinct and is evidently not due to thyroglobulin that may be in complex with the thyroid antibody.