The reduction of functional renal mass is known to induce the compensatory renal growth. Although the mechanism has not been fully elucidated, the humoral factors are considered to participate in it. In this study, the humoral factors were investigated on the rats, the renal mass of which were reduced by the subtotal ligation of renal arteries lieving one of the third branches of unilateral kidney. The effects of the plasma of uremic rats on the DNA synthesis were measured by the isotopic thymidine incorporation into DNA of renal cortex slice The plasma of uninephrectomized rats produced the stimulation of DNA synthesis, which was inhibited by adding the plasma of subtotally nephrectomized rats. By the dialysis of the uremic plasma with cellophane membrane or by the adsorption with the charcoal adsorbent (AST420), the inhibitory effects were markedly decreased. The uremic toxin fraction 2a obtained with the high performance liquid chromatography exerted the inhibitory effects on the DNA synthesis. The administration of AST-120 orally to the uremic rats reduced the hight of peak 2a and increased the stimulatry effects of the plasma on DNA synthesis. These results indicate that the renal growth factor in the plasma of rats with reduced renal mass is inhibited by the uremic toxins, the elimination of which by the adsorbent could increase the action of the growth factors.
