DEMONSTRATION OF AN ORGAN-SPECIFIC MITOTIC INHIBITOR IN AMPHIBIAN KIDNEY . EFFECTS OF ADULT XENOPUS TISSUE EXTRACTS ON MITOTIC RATE OF EMBRYONIC TISSUE (IN-VITRO)

Using the Colcemid metaphase arrest technique it was shown that extracts of adult Xenopus kidney inhibited mitosis in cultured larval pronephros but not in epidermis and that extracts of other organs had no significant effect on mitotic rate in the pronephros. The two stress hormones adrenalin and hydrocortisone inhibited mitotic activity both in pronephros and in epidermis and also enhanced the inhibitory effects of kidney extracts upon the pronephros. A mitotic inhibition of up to 50% was achieved by adding the extract obtained from 10 mg of tissue to 1 ml of the medium in which the larval pronephros was cultured. The biological role of this tissue-specific inhibitor or kidney chalone" may be to limit developmental growth and to maintain mitotic homeostasis in the mature kidney. © 1969."