Effect of age on kidney hyperplasia in the rat during cold acclimation.

In adult rats acclimated to 5 degrees C, the kidney weight increases with the length of the exposure. Kidney cells of younger rats survive explantation better than the cells of control rats of the same age. Kidney cells of older rats after cold acclimation and after unilateral nephrectomy have a lower vitality in vitro than corresponding control cells. Unilateral nephrectomy performed in rats aged 3 and 6 months, exposed previously to low temperature, leads to a better survival of explanted kidney cells than nephrectomy or cold only. Old rats do not survive exposure to 5 degrees C for more than 18 hr.