Background: Unilateral ureteral obstruction (UUO) of rats is a well-established model for studying obstructive nephropathy. Meanwhile, pathophysiology of pediatric obstructive nephropathy is not well understood. In this report, we studied monocyte/macrophage infiltration and expression of intercellular adhesion molecule 1 (ICAM-1) and macrophage antigen 1 (Mac-1) in weanling rats with UUO.
Methods: Three-week-old male Sprague-Dawley rats underwent left unilateral ureteral ligation. Both obstructed kidneys (OBK) and contralateral kidneys (CLK) were harvested at 3, 6, 12, 24, 72 and 120 h after surgery. Monocyte/macrophage infiltration and expression of ICAM-1 and Mac-1 were evaluated immunohistochemically, and results were compared with those of sham-operated control rats (SOK).
Results: Monocyte/macrophage infiltration was observed in the interstitium and perivascular region in the cortex of OBK within 6 h. The CLK and SOK showed slight monocyte/macrophage infiltration. Expression of ICAM-1 was markedly observed in the periarterial and peritubular interstitium and in renal cortical peritubular capillaries 12 h after obstruction. In CLK and SOK, ICAM-1 was slightly expressed in the endothelium of microvessels and parietal linings of Bowman's capsule. Expression of Mac-1 was detected mainly in cells infiltrating the perivascular interstitium in OBK. In CLK and SOK, few Mac-1-positive cells were observed.
Conclusions: Adhesion molecules, ICAM-1 and Mac-1, are expected to recruit monocyte/macrophage infiltration into OBK of weanling rats with UUO.