Effect of age on kidney hyperplasia in the rat after unilateral nephrectomy

The absolute weight of the rat's kidney increases from 3 weeks to 3 months and from 3 months to 12 months. The relative weight decreases. The number of cells freed from the kidney by trypsinization increases. (2) After nephrectomy, the kidney weight increases in all age groups. The increase is mery high in the youngest rats, lower but still significant in the 3 month old rats and still lower in the 12 month old rats. The number of cells freed from the kidney after nephrectomy is again very high in the young and 3 month old rats, but very low in the 12 month old rats. In these animals, the cell number is lower after nephrectomy than before, and a greater vulnerability of the cells is suggested as the cause of this phenomenon.