Transforming growth factor-beta (TGF-beta), a regulatory cytokine expressed in the kidney, plays a role in nephrogenic repair. This study utilized a chemical model of renal proximal tubule cellular injury and regeneration to investigate the effects of TGF-beta 1 on regeneration. Confluent monolayers of rabbit renal proximal tubular cells (RPTC) in primary culture exposed to the oxidant t-butylhydroperoxide (800 microM TBHP) for 1.5 hours were 24% confluent after 24 hours. Confluency increased to 50% 4 days after TBHP exposure. Recovery of monolayer confluency was associated with increased monolayer protein but not with DNA content. Daily treatment of injured monolayers with TGF-beta 1 inhibited the recovery of monolayer confluency and inhibited recovery of protein content in a concentration-dependent manner (0.02-1 ng/mL). DNA content of injured monolayers was not altered by TGF-beta 1. A single treatment of injured monolayers with 0.2 ng/mL (8 pM) TGF-beta 1 inhibited recovery of monolayer confluency and protein content without altering monolayer DNA content. These data show that a single 24 hour exposure to a low concentration (8 pM) of TGF-beta 1 inhibits regeneration of renal proximal tubule cell monolayers following oxidative injury by inhibiting, in part, cellular migration/spreading.