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

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Abstract
Earlier investigations about the consequences of experimental kidney ischemia raised the question of whether 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. Homogenates, or their separated fractions from infarcted or regenerated kidneys of adult donors and from kidneys of juvenile donors were directly injected into the left kidney parenchyma of receiver animals. A small dose of kidney homogenate produced 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 was of short duration, kidney-specific and not reproduced in different controls. The mitogenetic effect of a unilateral intrarenal dose of kidney homogenate did not favor a special area. Without a recognizable principle of cellular selection it occurs everywhere in the kidney parenchyma. It was understood as a simple increase of normal growth. The proliferation stimulus was humorally transmitted to the untouched contralateral kidney. Mitotic activity was significantly higher in the left than in the right kidney. A much better efficiency of the sediment, especially of the mitochondrial and microsomal fraction, than of the supernatant was found. 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.