Comparative studies of cellular reactions to injuries between the inner medulla and the cortex of rat kidneys.

The inner medulla and the cortex of the rat kidney were surgically traumatized or threaded with a silk suture, and the sequence of morphologic events occurring in these two topographic locations were studied by light microscopy on Days 7, 14, and 28. On Days 7, 14, and 28 following the infliction of the surgical trauma, such cellular reactions as mononuclear cell infiltration and fibroblastic proliferation were less intense in the injured site of the inner medulla than in the cortex. Numerous foreign body type giant cells appeared about the suture material in the cortex as early as Day 7 and were persistently present on Days 14 and 28. A similar type of foreign body giant cells did not appear about the suture material within the inner medulla throughout the experiment. Our results suggest that there is a difference in cellular reaction to injury or to a foreign body between the inner medulla and the cortex of rat kidneys.