Cephaloridine toxicity in primary cultures of rat renal cortical epithelial cells

Primary cultures of rat renal cortical epithelial cells were used to assess the in vitro nephrotoxicity of cephaloridine (Cph). Several different indices were used to follow the course of Cph-induced nephrotoxicity in the cultures. Plasma membrane integrity was determined by the effect of Cph on lactate dehydrogenase (LDH) leakage, cellular K(+) content and plasma membrane Na(+)/K(+) ATPase activity. Significant LDH leakage and decreased cellular K(+) content occurred after 8 hr of exposure to Cph. Na(+)/K(+) ATPase activity was depressed as early as 4 hr after Cph treatment. Brush border integrity was assessed by the effect of Cph on the activity of the brush border enzyme alkaline phosphatase, which was significantly decreased following 12 hr of exposure to Cph. Treatment with Cph resulted in an initial elevation of cellular glutathione (GSH)-as indicated by cellular non-protein sulphydryl content-followed by a decrease in GSH content 16 hr later. The mitochondrial response to Cph was assessed by determining mitochondrial succinate dehydrogenase (SDH) activity and cellular ATP content. SDH activity was significantly depressed after 4 hr of Cph exposure; ATP content was not significantly depressed until 12 hr after treatment. The time course of Cph-induced injury in our culture system suggests that early injury involves alterations at the level of the mitochondrial membrane and the plasma membrane. The most sensitive indicators of Cph-induced toxicity in this system were mitochondrial SDH activity and plasma membrane Na(+)/K(+) ATPase activity.