Influence of Prolactin on Thyroxine-Induced Changes in Hepatic and Tail Enzymes and Nitrogen Metabolism in Rana catesbeiana Tadpoles 1

Summary

Thyroxine administered either alone or in conjunction with prolactin caused a decrease in hepatic protein concentration and an increase in hepatic glutamic dehydrogenase activity and specific activity in Rana catesbeiana tadpoles. Hepatic lactic dehydrogenase activity is decreased after thyroxine treatment, while prolactin alone caused an increase in the activity and specific activity of this enzyme, Tail lactic dehydrogenase activity, on the other hand, increased following thyroxine treatment. Thyroxine-treated animals were shown to have increased urea excretion which is prevented when prolactin is simultaneously administered, confirming the findings of Medda and Frieden (5). On the other hand, the pattern of ammonia excretion is identical in tadpoles treated with thyroxine or prolactin plus thyroxine.

The possibility of a prolactin-thyroxine antagonism in mammals was examined in rats. It was found that prolactin, in the dose administered, had no antagonistic action on thyroxine-induced precocious eye opening.