Early recovery of the actin cytoskeleton during renal ischemic injury in vivo.

The actin cytoskeleton of proximal tubule cells is important for both the maintenance of membrane domains and attachment to neighboring cells and underlying substrata. Adenosine triphosphate (ATP) depletion during ischemic injury causes early alterations in the actin cytoskeleton, resulting in loss of membrane domains and cellular attachment. We examined the actin cytoskeleton during recovery from ischemic injury. As shown previously in cell culture studies, ATP depletion to 14% of control values from in vivo ischemia resulted in decreases in G-actin consistent with net polymerization of the cytoskeleton. After 20 minutes of recovery restored ATP levels to 24% of control values, percent G-actin increased back to control values, yet cytoplasmic actin polymerized with little evidence of apical recovery. After 120 minutes of recovery, ATP levels had increased to 48% of control values with little qualitative or quantitative change in actin polymerization from 20 minutes of recovery. When ATP levels recovered to 65% of control values at 360 minutes after ischemia, movement of F-actin back toward the apical surface was observed. These data, along with prior data using maleic acid, suggest that thresholds of cellular ATP may cause differing effects on distinct cellular actin pools. We conclude that actin cytoskeletal recovery occurs very early and may be necessary for reestablishment of polarity essential for normal reabsorptive functions.