CELL PROLIFERATION AND DNA SYNTHESIS AFTER UNILATERAL NEPHRECTOMY AS RELATED TO AGE

The effect of unilateral nephrectomy on DNA synthesis, as measured by tritiated thymidine autoradiography, and on mitotic index in both weanling and adult rat was measured. In the weanling rat group, the control animals showed a base line thymidine index (number of labeled cells per 50 oil immersion fields) of 74, and the adult animals an index of 9.6. In response to unilateral nephrectomy a peak value of 447 was obtained in the weanling animals and 98 in the adult animals, both peaks occurring at 36 hours. Mitotic counts were 7 in the weanling control animals and 0.5 in the adults, with a peak at 36 hours of 37 and 7, respectively. Separate counts of tubule and stromal cells in the cortex revealed that the increase in labeling occurred later in the stromal cells than in the tubule cells, the stromal cells not reaching a maximum until 57 hours after nephrectomy. The results indicate that although the relative rate is much lower in adult animals, a similar response, qualitatively, is obtained in both groups following unilateral nephrectomy. The findings also indicate that the stromal cells respond in a different fashion to the stimulus of unilateral nephrectomy and appear to lag behind the response of the tubule cells. (Author)