Objective To observe the effects of puromycin aminonucleoside (PAN) and dexamethasone (DEX) on the expression and distribution of podocin in vitro, and to explore the possible mechanism of DEX in improving proteinuria. Methods Mouse podocyte cells (MPCs) in control group were cultured with RPMI-1640 plus 0.02% DMSO, and were subjected to PAN treatment alone (PAN group) or PAN plus DEX (DEX group) for 8, 24,48 hours respectively. The podocyte morphology was observed by phase-contrast microscope, and was analyzed by Image J. The distribution, mRNA and protein expression of podocin were detected by indirect immunocytofluorescence, semi-quantitative RT-PCR and Western blot, respectively. Results The well-developed arborization and interconnection of podocytes were found in control group. PAN treatment led to significant shrinkage of podocytes with decreased distribution at 43% of control group at 8 h, 10% at 24 h and 5.7% at 48 h (P<0.01), respectively, together with podocyte foot process retraction as well as effacement and loss of cell contact. RT-PCR revealed podocin mRNA expression prone to decrease. Western blot showed podocin protein expression was significantly decreased and immunocytochemistry revealed podocin expression was disappeared in the cellular membrane after PAN treatment. DEX significantly prevented the shrinkage of podcytes, with decreased area at 43.9% of control at 8 h, 26.2% at 24 h and 29.6% at 48 h (P<0.05), respectively, and up-regulated the mRNA and protein expression of podocin at 48 h (P<0.05). The abnormal distribution of podocin was also alleviated by DEX. Conclusion DEX exerts a direct action on podocyte via stabilizing mRNA, protein expression and distribution of podocin, which may be associated with the improvement of proteinuria.