Ischemic induced cell injury results in rapid duration-dependent ADF/cofilin mediated disruption of the apical microvilli microfilament cores. Since intestinal microvillar microfilaments are bound and stabilized in the terminal web by the actin binding protein, tropomyosin, we questioned if a protective effect of tropomyosin localization to the terminal web of the proximal tubule microfilament cores is disrupted during ischemic injury. With tropomyosin specific antibodies we examined rat cortical sections under physiological conditions and following ischemic injury by confocal microscopy. In addition, Western blot analysis of cortical extracts and urine was undertaken. Our studies demonstrated the presence of tropomyosin isoforms in the proximal tubule microvillar terminal web under physiological conditions and their dissociation in response to twenty-five minutes of ischemic injury. This correlated with the excretion of tropomyosin containing plasma membrane vesicles in urine from ischemic rats. In addition, we noted increased tropomyosin Triton X-100 solubility following ischemia in cortical extracts. These studies suggest tropomyosin binds to and stabilizes the microvillar microfilament core in the terminal web under physiological conditions. With the onset of ischemic injury, we propose tropomyosin dissociates from the microfilament core providing access to microfilaments in the terminal web for F-actin binding, severing and depolymerizing actions of ADF/cofilin proteins.