Early response of the hamster kidney to cold exposure and unilateral nephrectomy

1. 1. Renal enlargement and DNA synthesis were studied in adult male hamsters at 1-5 days and at 2 weeks following either unilateral nephrectomy or cold exposure (4°C) alone or in combination. 2. 2. Either treatment alone caused a 40-45 per cent increase in renal wet weight within 2 weeks. When the treatments were combined the effects were additive. 3. 3. Per cent dry weights were decreased only in cold-exposed hamsters after 2 weeks of treatment. 4. 4. Renal cortical DNA synthesis, as determined by the use of radioautography after the injection of tritiated thymidine, was increased significantly at 2 days after unilateral nephrectomy, at 14 days after cold exposure and at 5 and 14 days when animals received the combined treatment. 5. 5. DNA synthesis in the outer medulla was increased significantly at 2 weeks after cold exposure and at 3, 5 and 15 days after both unilateral nephrectomy and exposure to the cold. 6. 6. Within the inner medulla only the combined treatment for 14 days caused a significant increase in DNA synthesis in tubular epithelia.