Abstract

A possible thyroidal control of water balance in the leopard frog, Rana pipiens, was investigated by (1) chemically thyroidectomizing intact animals by chronic injections of the goitrogen, 6-n-propyl-2-thiouracil (PTU ), or making animals hyperthyroid with thyroxine injections, and (2) dehydration of the frogs in a flow of air to enhance the rate of water loss through the skin, followed by rehydration in tap water until the animals regained their former weight. Radioiodine was employed in limited studies on the frog thyroid gland to ascertain the effects on thyroidal function caused by PTU. The frogs were dehydrated in desiccators in which there was a constant flow of clean, dry air over the animals. The cloacas cf the anurans were sutured closed during light etherization, and the frogs were weighed at regular intervals during dehydration and rehydration to determine the water loss and regain through the skin. PTU-treated frogs generally exhibited greater mean values for rates and total amounts of water loss and regain through the integument, and in one experiment, the PTU animals had a statistically greater rate of dehydration when compared to control frogs. The data indicated, however, that a goitrogen-induced, thyroxine depletion was not the cause for this increased, two-directional water movement through the frog skin, so several alternative proposals were therefore offered to explain the results obtained. The radioiodine studies demonstrated that the thyroid glands of normal, winter R. pipiens contained roughly 42 % 3-monoiodotyrosine, 28 % 3,5-diiodotyrosine, 21 % inorganic iodide, 6 % thyroxine, and 3 % origin material, and that the accumulation of radioiodine by these glands was approximately 2 % of the injected dose. PTU decreased the accumulative radioactivity of the frog thyroids to about 0.6 % of the injected quantity, markedly hindered the iodination of tyrosines, and depressed the level of thyroxine production, but this goitrogen did not completely inhibit thyroidal function.

Degree

College and Department

Life Sciences; Plant and Wildlife Sciences

Rights

http://lib.byu.edu/about/copyright/