Preplaced cell division - A critical mechanism of protection against S-1,2-dichlorovinyl-L-cysteine-induced acute renal failure and death in mice. Am J Physiol Renal Physiol 000 - 000, 2006. Previous studies have shown that renal injury initiated by a lethal dose of S-1,2-dichlorovinyl-L-cysteine (DCVC) progresses due to inhibition of cell division and hence renal repair, leading to acute renal failure (ARF) and death in mice. Renal injury initiated by low to moderate doses of DCVC is repaired by timely and adequate stimulation of renal cell division, tubular repair, restoration of renal structure and function leading to survival of mice. Recent studies have established that mice primed with a low dose of DCVC (15 mg/kg, ip) 72 h before administration of a normally lethal dose (75 mg/kg, ip), are protected from ARF and death (nephro-autoprotection). We have shown that renal cell division and tissue repair stimulated by the low dose are sustained even after the lethal dose administration resulting in survival from ARF and death. If renal cell division induced by the low dose is indeed the critical mechanism of this autoprotection, then its ablation by the antimitotic agent colchicine (1.5 mg CLC/kg, ip) should abolish autoprotection. The present interventional experiments were designed to test the hypothesis that DCVC autoprotection is due to stimulated cell division and tissue repair by the priming low dose. CLC intervention at 42 & 66 h after the priming dose resulted in marked progressive elevation of plasma blood urea nitrogen (BUN) and creatinine resulting in ARF and death of mice. Light microscopic examination of H&E stained kidney sections revealed progression of renal necrosis concordant with progressively failing renal function. With CLC intervention, S phase stimulation (as assessed by BrdU pulse labeling), G₁ to S phase clearance, and cell division were diminished essentially abolishing the promitogenic effect of the priming low dose of DCVC. Phospho-retinoblastoma protein (P-pRB), a crucial protein for S phase stimulation, and other cellular signaling mechanisms regulating P-pRB, were investigated. We report that decreased P-pRB is the critical mechanism of this inhibited S phase stimulation and ablation of autoprotection with CLC intervention. These findings lend additional support to the notion that stimulated cell division and renal tissue repair by the priming dose of DCVC is the critical mechanism that allows sustained compensatory tissue repair and survival of mice in nephro-autoprotection.