THE ROLE OF PROLACTIN IN THE SLOUGHING CYCLE OF THE LIZARD, GEKKO GECKO L.

Abstract

SUMMARY Prolactin injected into hypophysectomized geckos restored the length of the sloughing cycle to normal (about 35 days) when given in doses of 0·26 i.u./g body wt on alternate days. When the doses of prolactin were increased to 0·4 i.u. the length of the sloughing cycle was reduced to about 30 days. Prolactin given to thyroidectomized geckos shortened the length of the sloughing cycle to about 28 days when administered in doses of 0·4 i.u./g on alternate days. Prolactin probably acts directly on the epidermis and not through the thyroid gland, since prolactin restored sloughing in thyroidectomized animals. Moreover, prolactin had no effect on the activity of the thyroid gland in the hypophysectomized animals as judged by the percentage uptake of 131I or the histological structure. Prolactin in doses of 0·4 i.u./g on alternate days reduced the length of the resting phase of the sloughing cycle; the renewal phase remained unaltered.