Regulation of compensatory kidney hypertrophy by its own products.

1. The ligation of blood vessels of one kidney of adult rats resulted in the compensatory hypertrophy of the other kidney. In most animals the rate of hypertrophy was indistinguishable from that observed after unilateral nephrectomy, but in a few cases the onset was retarded when the renal artery alone had been ligated and the collateral circulation increased.2. When the blood vessels of one kidney of adult rats were ligated and the cortex was excised, the rate of compensatory renal hypertrophy was similar to that observed after unilateral nephrectomy.3. In animals operated for simultaneous partial hepatectomy and unilateral nephrectomy, there was no sign of compensatory renal hypertrophy while the liver was undergoing regeneration. Renal hypertrophy started after 7 days, when about 98% of the amount of liver removed had been regenerated.4. Neither aseptic autolysis of one kidney following suppression of its blood supply, nor unilateral nephrectomy affected the rate of liver regeneration after simultaneous partial hepatectomy.5. Total splenectomy did not affect the rate of compensatory renal hypertrophy following unilateral nephrectomy.6. The heterotopic graft of renal cortical, but not of medullary, cells inhibited compensatory renal hypertrophy in adult rats. The removal of the graft after 14 days was followed by the resumption of compensatory hypertrophy.7. The inhibiting action of fractions of renal cortical extracts fractionated on Sephadex G100 resin and DEAE-52 cellulose were assayed on the ;growth' of renal explants reared in vitro. The final material, though only partially purified, proved to have an inhibiting activity between 250 and 500 times greater than that of the initial extract.8. When injected into unilaterally nephrectomized rats, the partially purified extract from the renal cortex had an inhibiting effect on compensatory renal hypertrophy.9. Immunofluorescence technique showed that the partially purified cortical extract affected the proximal convoluted tubes specifically, irrespective of animal species.