[Compensatory hypertrophy of the kidney. I. - Search for the existence of a renal inhibitory substance (author's transl)].

In view of the theory of autoregulation of cell multiplication in a growth organ, we attempted to inhibit renal tubular cell hyperplasia in the remaining kidney 48 hours after controlateral nephrectomy. To do this we drew up a method of measurement of hyperplasia by measuring the rate of uptake of tritiated thymidine in the organ undergoing compensatory growth. We then injected renal cytosol. Whereas the rate of uptake of tritiated thymidine doubles in the growing kidney compared with control animals, the intravenous administration of renal cytosol reduces the renal uptake of the tracer to its basal level. We correlated this observation with the microscopic count of mitotic figures, and noted the existence of parallel fluctuations. Our results seem to support the initial working hypothesis but they do not exclude the possibility of a more complex regulatory mechanism in which serum stimulant factors may also play a role.