Fluctuating shear stress effects on stress fiber architecture and energy metabolism of cultured renal cells.

The project investigates the relationship between the external shear force and the actin cytoskeleton along with the metabolic changes occurring inside the cells due to this force. Anchorage-dependent Madin Darby canine kidney (MDCK) cells were placed in spinner flasks with paddle-type stirrers agitated at 20 rpm, where they experienced shear stress fluctuations from 0.02 to 0.27 dyn/cm2 in magnitude. Following fixation, permeabilization, and staining with rhodamine-phalloidin, the relative amounts and distribution of F-actin stress fibers in the 1 micron basal layer of the cells were visualized by confocal microscopy. These structures disappeared after 12-15 h of exposure to shear stress. Previous results showed that the stress fibers disappear, leading to loss of epithelial attachment, after only 1 h of starvation-induced energy depletion. Therefore, in this study, the energy metabolism of the cells was established by measuring adenosine triphosphate (ATP) levels at different time intervals. No statistical difference in ATP content was found between the shear-stressed cells and the controls, showing that shear stresses cause cytoskeletal reorganization by a mechanism other than ATP depletion.