Effect of Xenoplastic Adrenal Transplants upon Limb Regeneration in Normal and Hypophysectomized Newts (Triturus viridescens)

1. Our previous experiments showed that recuperation of regeneration in limbs of hypophysectomized newts may be obtained by replacement therapy with ACTH and with adreno-cortical hormones. We tested the hypothesis that an hyperadrenal state is necessary for regeneration. The study of effect of xenoplastically transplanted single or multiple adrenal frog glands upon regeneration of the fore limb in previously hypophysectomized newts was the method used. Control experiments showing that frog muscle tissue and also other tissues transplanted under similar conditions had no effect upon the non-regeneration typical for hypophysectomized newts indicated that xenoplastic transplants per se produced no observable effects upon regeneration. Frog adrenals, however, while not affecting regeneration in normal animals were found capable of restoring to hypophysectomized newts the ability to regenerate amputated limbs otherwise lost after extirpation of the pituitary. 2. Hypophysectomized animals are more susceptible to adrenal therapy 10 to 20 days after amputation than during earlier periods, since it is when transplanted at this time that frog adrenals most consistently produced regeneration. These results while not clearly understood, point to the existence of a critical stage within the post-amputational phases of regeneration when regeneration is particularly susceptible to adrenal hormones, endogenous or experimentally supplied. 3. Heretofore unsuspected involvement of adrenal secretions in limb regeneration of newts is thus demonstrated and the pituitary-adrenal synergism discovered for conditions of “stress” in mammals acquires a new importance for regenerative processes in amphibia.