Abstract
The effect of accelerating metamorphosis with two different doses of L-thyroxine on the epidermal ATPase activity of Rana catesbeiana tadpoles was examined. Na, KATPase activity progressively increased in epidermis of tadpoles treated with 10ng/ml of thyroxine and at the end of the experimental period the value was around 5 times the control group. In the group of tadpoles treated with 100ng/ml of thyroxine, activity of this enzyme changed more rapidly reaching values 7 times the control on the 10th day of treatment. The effect of thyroxine treatment on epidermal content of Mg-ATPase in tadpoles was considerably less than the changes noted above for Na, K-ATPase; levels after 10 days of treatment were only twice control values. In contrast to its effect in tadpoles, thyroxine treatment effected neither ATPase activity nor oxygen consumption of epidermal tissue from adult Rana pipiens frogs. From these observations it might be concluded that Na, K-ATPase activity of frog skin is specifically dependent on thyroid hormones for its initial activation (during metamorphosis) but not its subsequent control.
