Changes in laminin during recovery from postischemic acute renal failure in rats

Changes in the immunoreactivity of laminin have been demonstrated in a variety of tissues undergoing injury-regeneration process and during nephrogenesis. Studies in vitro revealed that laminin is important in many cellular functions such as growth, differentiation, and cell communication. This study examined the changes of laminin in the extracellular matrix (ECM) of proximal straight tubules (PST) in the outer stripe of the outer medulla after renal ischemia, an area where most morphological damage occurred. Anesthetized male Sprague-Dawley adult rats underwent a 30-min temporary occlusion of the left renal artery. The inulin clearance (Cin) of the postischemic left kidneys was significantly decreased at 30 min, 1 day, 2 days, and 5 days after the injury, and at 7 and 10 days after the injury it rose to a level not significantly different from the sham-operated controls. Using immunogold electron microscopy, the density of immunoreactive laminin (gold-conjugated laminin grains/micron2 ECM area) in PST where flattened PST cells were present was decreased at 1 day and 2 days, and at 5 days, a time when the renal function was still depressed, it returned to a level not significantly different from that in controls. These changes were not observed in those PST or proximal convoluted tubules in which morphology was intact. Further studies are needed to determine if these changes in laminin of damaged PST cells have any significant role during their recovery from the ischemic injury.