THE EFFECT OF ACTH ON THE SLOUGHING FREQUENCY OF NORMAL AND THYROIDECTOMIZED ANOLIS CAROLINENSIS (IGUANIDAE, LACERTILIA)

¹ Department of Biology, The Catholic University of America, Washington, D. C. 20017

The effect of thyroidectomy and administration of ACTH (0.4 I.U. on alternate days) on sloughing performance in normal and thyroidectomized Anolis has been investigated. Either thyroidectomy or injection of ACTH decreases the frequency of sloughing, but does not inhibit it. ACTH administration and thyroidectomy together prevent sloughing. Histological study of the skin shows that the resting phase of the sloughing cycle is lengthened in thyroidectomized animals and in intact animals receiving ACTH injections, and is indefinitely prolonged in thyroidectomized animals injected with ACTH. Hyperkeratosis (increase in the thickness of the keratin layer) is observed in all animals with a protracted cycle, except in thyroidectomized animals with ACTH administration. Since there is no difference in the I¹³¹ uptake or in the histological appearance of the thyroid gland following ACTH treatment, it is suggested that ACTH influences the sloughing cycle independently of the thyroid gland probably through a direct inhibitory effect on cellular proliferation.