Increase of mitosis in the tubular epithelium following intrarenal doses of various kidney homogenates and hemogenate fractions in the rat.

Earlier investigations about the consequences of experimental kidney ischemia raised the question, if there exists a substance in the renal tissue which is liberated by cell death or during regeneration of cells and which might stimulate mitosis of other cells. Therefore in recent experiments we directly injected into the left kidney parenchyma of receiver animals, homogenates, or their separated fractions from infarcted or regenerated kidneys of adult donors and from kidneys of juvenile donors. These are the results" 1. A small dose of kidney homogenate already produces a clear increase of mitoses in the tubular epithelium of the renal cortex 17-19 h after injection in the adult recipient of the same breed. The increase of proliferation is of short-duration, kidney-specific, and not to reproduce in different controls. 2. The mitogenetic effect of a unilateral intrarenal dose of kidney homogenate does not favor a special area. Without a recognizable principle of cellular selection it occurs everywhere in the kidney parenchyma. It must be understood as a "simple increase" of normal growth. The proliferation stimulus is humorally transmitted to the untouched contralateral kidney. Yet the mitotic acitivty is significantly higher in the left than in the right kidney. 3. The experiments demonstrate a much better efficiency of the sediment, especially of the mitochondrial and microsomal fraction, than of the supernatant. 4. Our results indicate that in the complicated regulation system of cell growth there must be taken into account different factors and signalizing ways for induction and termination of mitosis.