Effects of kidney extract on the folic acid induced proliferation of the rat kidney.

Single injection of a high dose of folic acid causes a proliferation of the kidney with an increase of the 3H-thymidine incorporation into the DNA of kidney cortex slices in rats. An aqueous extract from rat kidneys inhibits the increase of 3H-thymidine incorporation. The inhibition begins after 4 hours. The maximum effect is observed between 11 and 17 hours after injection of the kidney extract. The kidney extract also inhibits the increase of the DNA content per kidney after folic acid injection. Heart, lung, spleen and liver extracts and bovine serum albumin do not lead to inhibition of the 3H-thymidine incorporation into the DNA of kidney cortex sclices.