EFFECTS OF PROLACTIN ON THYROIDECTOMIZED BUFO BUFO LARVAE

SUMMARY Young Bufa bufo larvae (Rossi's stage V to VII), were thyroidectomized by means of a single dose of I131 (20 μC). Starting on the 37th day after radioactive iodine treatment, these larvae were given a daily injection of 0.3 I.U. of pure ovine prolactin (Richter) for 14 days. As compared to untreated larvae, prolactin-treated ones underwent a statistically significant (P < 0.001) higher loss in body weight during their last week of life; they exhibited a less marked degranulation of both the acidophilic cells that are regarded as producing a prolactin-like hormone, and of the thyrotropic cells. The possibility of some direct inhibitory effect being exerted by prolactin on the pituitary cells in correlation with the incomplete development of the hypothalamo-hypophysial axis, due to thyroidectomy, is discussed. In the integument, exogenous prolactin seems to have enhanced the differences brought about by thyroidectomy with respect to normal larvae (i.e. further gland rudiment reduction and more unifo...