HEAT-STRESS AMELIORATES ATP DEPLETION-INDUCED SUBLETHAL INJURY IN MOUSE PROXIMAL TUBULE CELLS

The role of prior heat stress (HS) in ameliorating changes in the acti n cytoskeleton and the loss of tight junction integrity that accompany ATP depletion was examined. Mouse proximal tubule cells in primary cu lture were exposed to sodium cyanide (CN) in the absence of dextrose f or 1 h, a maneuver that produced equivalent degrees of ATP depletion i n control and in HS cells. After ATP depletion, actin stress fibers we re completely disrupted in control cells. In contrast, HS cells with e levated HSP-72 content showed preservation of stress fibers after CN e xposure. ATP depletion in control and HS cells produced similar and re versible depletion of the G-actin pool without altering total actin co ntent. Integrity of the tight junction was assessed by transepithelial electrical resistance (TER) and unidirectional flux of lucifer yellow (LY, mol wt 482). After CN alone, the nadir in TER was lower than tha t of HS + CN cells (51.6 +/- 2.5 vs. 96.2 +/- 3.2 Ohm . cm(2), respect ively; P < 0.05). After 30-min recovery, TER of HS + CN recovered to c ontrol values (277 +/- 7.2 vs. 227 +/- 6.6 Ohm . cm(2); P > 0.05), whe reas CN did not (165 +/- 7.3 vs. 227 +/- 6.6 Ohm . cm(2); P < 0.05). C hanges in LY flux paralleled those in TER. HS is associated with prese rvation of the actin cytoskeleton and improved integrity of the tight junction after sublethal ATP depletion injury. These protective effect s may contribute to the preservation of epithelial cell polarity and f unction following an ischemic insult.