Rapid reversal of compensatory renal hypertrophy after withdrawal of the stimulus.

The permanence of the early phases of compensatory renal hypertrophy was tested by interrupting vascular parabiosis between an anephric rat and a normal rat after 48 hours. At the time of interruption, the weights and the ratio of ribonucleic acid (RNA) content to deoxyribonucleic acid (DNA) content of the kidneys were the same as those of the remaining kidney in a single rat subjected to unilateral nephrectomy, previously reported. Within 12 hours after parabiosis was stopped, renal mass and nucleic acid concentrations returned to normal. Compensatory hypertrophy could be produced again by unilateral nephrectomy. Regression of the early phase of compensatory hypertrophy appears to be faster than muscular atrophy produced by disuse or denervation. Compensatory hypertrophy can be activated at least twice.