No abstract

The addition of L-ascorbic acid 2-phosphate (AscP) to primary cultures of rabbit renal proximal tubular cells (RPTC) grown under improved culture conditions resulted in an extended growth phase and increased cellular density (1.3-fold increase in monolayer DNA and protein contents). AscP reduced glycolysis, increased net lactate consumption by 38%, and stimulated net glucose production by 47%. Basal O2 consumption increased by 39% in RPTC grown in the presence of AscP and was equivalent to that in freshly isolated proximal tubules. AscP increased ouabain-sensitive O2 consumption (81%) and Na(+)-K(+)-ATPase activity (2.5-fold), which suggested increased active Na+ transport. Addition of AscP increased Na(+)-dependent glucose uptake by 43% and brush-border enzyme marker activities by 46%. It is concluded that supplementation of media with AscP further improves RPTC culture conditions by promotion of cellular growth and stimulation of in vivo-like respiration, lactate utilization, and net glucose synthesis. These changes are accompanied by an increase in brush-border enzyme activities and stimulation of active Na+ transport and Na(+)-dependent glucose transport, which demonstrate an improved expression of brush-border membrane functions in RPTC.

This study investigated the recovery of renal proximal tubule cellular (RPTC) functions following oxidant-induced sublethal injury. tert-Butylhydroperoxide (TBHP) treatment resulted in 24% cell death and loss 4 h following the exposure. The remaining sublethally injured RPTC proliferated, and monolayer DNA content returned to control values on day 4 following TBHP exposure. Basal oxygen consumption (Qo 2) and ATP content in sublethally injured RPTC were decreased 64 and 63%, respectively, at 4 h and returned to control values on day 6. Net lactate consumption decreased 71% at 4 h and returned to control values on day 4. In contrast, net glutamine consumption increased 2.7-fold at 4 h and returned to control values on day 6. Ouabain-sensitive Qo 2, Na+-K+-adenosinetriphosphatase (Na+-K+-ATPase) activity, and Na+-coupled glucose transport were inhibited 77, 88, and 83%, respectively, at 4 h and recovered to control values on day 6. These data show that 1) mitochondrial function, Na+-K+-ATPase activity, active Na+ transport, and Na+-coupled glucose transport are decreased in sublethally injured RPTC following oxidant exposure and are repaired over time; 2) monolayer regeneration precedes the recovery of mitochondrial and transport functions, and 3) sublethal injury and subsequent regeneration are associated with alterations in metabolic substrate utilization. These results suggest that oxidant-induced sublethal injury to RPTC may contribute to renal dysfunction and that RPTC can repair and regain cellular functions following oxidant injury.

This study examined the repair of renal proximal tubule cellular (RPTC) functions following sublethal injury induced by the nephrotoxicant S-(1,2-dichlorovinyl)-l-cysteine (DCVC). DCVC exposure resulted in 31% cell death and loss 24 h following the treatment. Monolayer confluence recovered through migration/spreading but not proliferation after 6 days. Basal, uncoupled, and ouabain-sensitive oxygen consumption (Qo 2) decreased 47, 76, and 62%, respectively, 24 h after DCVC exposure. Na+-K+-ATPase activity and Na+-dependent glucose uptake were inhibited 80 and 68%, respectively, 24 h after DCVC exposure. None of these functions recovered over time. Addition of epidermal growth factor (EGF) following DCVC exposure did not prevent decreases in basal, uncoupled, and ouabain-sensitive Qo 2 values and Na+-K+-ATPase activity but promoted their recovery over 4–6 days. In contrast, no recovery of Na+-dependent glucose uptake occurred in the presence of EGF. These data show that: 1) DCVC exposure decreases mitochondrial function, Na+-K+-ATPase activity, active Na+ transport, and Na+-dependent glucose uptake in sublethally injured RPTC; 2) DCVC-treated RPTC do not proliferate nor regain their physiological functions in this model; and 3) EGF promotes recovery of mitochondrial function and active Na+ transport but not Na+-dependent glucose uptake. These results suggest that cysteine conjugates may cause renal dysfunction, in part, by decreasing RPTC functions and inhibiting their repair.