ACTIN AND VILLIN COMPARTMENTATION DURING ATP DEPLETION AND RECOVERY IN RENAL CULTURED-CELLS

ATP-depletion in renal cultured cells has been used as a model for stu dying various cytoskeletal and functional alterations induced by renal ischemia. This communication explores the reversibility of these effe cts utilizing a novel method [1] that depleted ATP (ATP-D) to 2% of co ntrol within 30 minutes and caused complete recovery (REC) of ATP in o ne hour. Under confocal microscopy, ATP-D (30 min) caused thinning of F-actin from the microvilli, cortical region, and basal stress fibers, with the concurrent appearance of intracellular F-actin patches. Thes e changes were more pronounced after 60 minutes of ATP-D. One hour of REC following 30 minutes of ATP-D produced complete recovery of F-acti n in each region of the cell. However, after 60 minutes of ATP-D, a he terogeneous F-actin recovery pattern was observed: almost complete rec overy of the apical ring and microvilli, thinned cortical actin with o ccasional breaks along the basolateral membrane, and a dramatic reduct ion in basal stress fiber density. The time course of cortical actin a nd actin ring disruption and recovery coincided with a drop and recove ry in the transepithelial resistance and the cytoskeletal dissociation and reassociation of the Na,K-ATPase. Additionally, the microvilli re tracted into the cells during ATP-D, a process that was reversed durin g REC. Triton extraction and confocal microscopy demonstrated that vil lin remained closely associated with microvillar actin during both ATP -D and REC. These distinctive regional differences in the responses of F-actin to ATP depletion and repletion in cultured renal epithelial c ells may help to clarify some of the differential tubular responses to ischemia and reperfusion in the kidney.