Partial characterization of a renotropic factor

In 70 experiments, the existence of a circulating renal growth factor was confirmed by 9.3% stimulation of 3H-thymidine into the DNA of renal fragments incubating for 90 min in the presence of sera from 20-hour unilaterally nephrectomized rats compared to sera from 20-hour sham-operated rats (p less than 0.001). Dialysis (7.4%, p less than 0.01) or removal of albumin (11.8%, p less than 0.001) from sera of both sham-operated and unilaterally nephrectomized rats did not appreciably change the magnitude of the statistically significant stimulation. When albumin-free sera were placed in boiling water for 1-3 min to coagulate protein, the stimulation was still significantly different from control (5%, p less than 0.05). Addition of sera from unilaterally nephrectomized rats (20 h) to isolated nuclei, even isolated nuclei removed from growing kidneys (72 h after unilateral nephroctomy), failed to enhance DNA synthesis significantly.