Stimulation of cell division in ectopic kidney grafts following unilateral removal of the lung.

Small fragments of kidney tissue were grafted into the right lung (Xenopus laevis) and the left lung was subsequently removed. This stimulated compensatory hyperplasia (increased mitotic rate) in alveolar tissue of the right lung and in the kidney graft. This suggests that the stimulus to compensatory hyperplasia is location-specific rather than tissue- or organ-specific. After implantation into the lung the kidney grafts are revascularized by the surrounding pulmonary supply. Damage or functional impairment of an organ usually produces a localized increase in the rate of blood flow and we therefore propose that this may lead to an increased rate of cell division in one of two ways: by permitting an increased functional capacity in the tissue concerned, or by causing a more rapid local clearance of mitotic control factors.