The purpose of this study was to investigate the effects of telmisartan (5 x 10(-5) M) on the mechanical response of left ventricular papillary muscle in rats with streptozotocin-induced diabetes mellitus. We studied 32 rats; 16 were rendered diabetic by a single intravenous injection of streptozotocin (45 mg kg(-1) i.v.) and 16 formed a non-diabetic control group. Diabetic animals were divided into two groups: diabetic-telmisartan group and the diabetic-control group. Non-diabetic controls were further divided into the non-diabetic-telmisartan group and the non-diabetic-control group. We found: (1) Muscle twitch tension (P-0) and contraction and relaxation rates were significantly lower in diabetic controls than in the other groups. (2) Telmisartan significantly increased P-0 in both diabetic and non-diabetic rats. (3) Times to peak tension and half-relaxation were significantly greater in groups DC and DT than in the non-diabetics. In conclusion, our data suggest that telmisartan attenuates diabetes-induced impairment of diabetic rat papillary muscles, and may thus be able to reduce cardiac complications in diabetes.