NEPHROTOXICANT INHIBITION OF RENAL PROXIMAL TUBULE CELL REGENERATION

Although nephrotoxicants have been shown to have direct lethal effects on renal proximal tubule cells (RPTC), little is known concerning their effects on the renal regenerative process. Additionally, the mechanisms of RPT regeneration are still not clear. To examine these issues, an in vitro model of mechanically induced injury to primary cultures of rabbit RPTC was developed, and the effects of epidermal growth factor (EGF), transforming growth factor-beta 1 (TGF-beta 1), and nephrotoxicants on the regenerative process were examined. Experiments demonstrated that confluent monolayers swiped with a 4-mm Teflon policeman regenerated with 77% closure of the swipe in 7 days. DNA content in swiped monolayers increased, reached a maximum on day 3 (1.4-fold), and remained constant through day 7. EGF accelerated regeneration and resulted in 96% swipe closure on clay 7 and increased DNA content 2.3-fold. TGF-beta 1 inhibited regeneration and resulted in 22% swipe closure on day 7 but did not inhibit the increase in DNA content. 5-Fluorouracil inhibited regeneration and resulted in 27% swipe closure on day 3, compared with 46% in the controls, and inhibited the increase in DNA content. Mercuric chloride, fumonisin B-1, and dichlorovinyl-L-cysteine, at concentrations less than or equal to 50% of their lethal concentration, inhibited regeneration and resulted in swiped areas 3.7, 4.2, and 2.1 times larger, respectively, than controls on day 7. At concentrations less than or equal to 50% of its lethal concentration, tert-butylhydroperoxide had no effect on swipe closure. These results suggest that proliferation and migration/spreading are important mechanisms in the regeneration process, that EGF expedites the regeneration, and that certain nephrotoxicants may contribute to renal dysfunction by inhibiting the RPT regeneration.