Apoptosis frequently occurs in acute renal injury but the molecular mechanisms responsible for this distinct form of cell death are largely unknown. Fas belongs to the tumour necrosis factor (TNF)/nerve growth factor superfamily and engagement by Fas ligand induces apoptosis in various epithelial cells. To investigate the role of apoptosis and associated mechanisms, we examined the occurrence of apoptosis and Fas and Fas ligand expression, and the therapeutic effect of alpha-melanocyte-stimulating hormone (alpha-MSH), a potent anti-inflammatory cytokine in an ischaemic acute renal failure (ARF) rat model. We also examined neutrophil infiltration together with intercellular adhesion molecule-1 (ICAM-1) expression because of their possible involvement in apoptosis due to their ability to release various inflammatory cytokines and reactive oxygen species.