The transmural heterogeneous changes of transient outward potassium currents (Ito) in rabbit hypertrophic cardiaomyocytes and the effects of long-term prophylactic treatment with volsartan were investigated. Rabbits were divided into hypertrophy group (left ventricular hypertrophy induced by partial ligation of abdominal aorta), vol-treated group (volsartan was administrated after the ligation), and control group (sham operated). Myocytes were isolated by a two-step enzymatical method. The sub-endocardial (Endo) and sub-epicardium (Epi) tissues were separated from midmyocardium (Mid) with a razor. Whole-cell patch-clamp technique was used to record potassium currents. The results showed that membrane capacitance was larger in hypertrophic cells than those in control and vol-treated cells (P＜0.01 vs control cells, n= 30). The densities of Ito in hypertrophic cells were reduced by sub-epicardium (Epi) (27.8 ± 2.9) %, midmyocardium (Mid)(41.0± 4.7) %, and sub-endocardium (Endo) (20.3 ± 3.4) % compared with those in control cells. The decrease of Ito density was more pronounced in Mid than in Epi and Endo (P＜0.01 vs Epi or Endo). There were no significant differences in Ito densities between vol-treated group and control group in three layers separately. In conclusion, volsartan can inhibit the transmural heterogeneous changes of Ito in left ventricular hypertrophic cardiomyocytes in rabbit.