OBJECTIVE: We have shown previously that exercise training enhances endothelium-dependent and endothelium-independent vascular relaxation in rabbit kidney. This study aimed to investigate protein expression changes in the rabbit renal cortex induced by chronic dynamic exercise. DESIGN: Kidneys were obtained from New Zealand rabbits either confined to pens (n = 8) or trained on a treadmill (0% grade) for 5 days/week at a speed of 18 m/min for 60-min periods over 12 weeks (n = 8). Expression of proteins in the renal cortex was determined by colloidal Coomassie blue staining after two-dimensional polyacrylamide gel electrophoresis. Differential protein spots were excised and digested with trypsin, and peptides were sequenced by electrospray ionization-ion trap mass spectrometry. RESULTS: Two pairs of matching differentially stained spots displayed an approximate threefold increase in trained compared with sedentary animals. These four spots presented a molecular mass of 23 kDa but different pI values. Mass spectrometric analyses revealed the pairs of matching spots as being rabbit apolipoprotein A-I. CONCLUSION: Chronic dynamic exercise increases apolipoprotein A-I expression in the rabbit renal cortex. This fact could be involved in the alterations observed in the renal circulation after exercise training.