Milk casein-derived angiotensin-converting enzyme (ACE)-inhibitory tripeptides isoleucine-proline-proline (Ile-Pro-Pro) and valineproline-proline (Val-Pro-Pro) have been shown to have antihypertensive effects in human subjects and to attenuate the development of hypertension in experimental models. The aim of the present study was to investigate the effect of a fermented milk product containing Ile-Pro-Pro and Val-Pro-Pro and plant sterols on already established hypertension, endothelial dysfunction and aortic gene expression. Male spontaneously hypertensive rats (SHR) with baseline systolic blood pressure (SBP) of 195 mmHg were given either active milk (tripeptides and plant sterols), milk or water ad libitum for 6 weeks. SBP was measured weekly by the tail-cuff method. The endothelial function of mesenteric arteries was investigated at the end of the study. Aortas were collected for DNA microarray study (Affymetrix Rat Gene 1.0 ST Array). The main finding was that active milk decreased SBP by 16 mmHg compared with water (178 (SEM 3) v. 195 (SEM 3) mmHg; P,0·001). Milk also had an antihypertensive effect. Active milk improved mesenteric artery endothelial dysfunction by NOdependent and endothelium-derived hyperpolarising factor-dependent mechanisms. Treatment with active milk caused mild changes in aortic gene expression; twenty-seven genes were up-regulated and eighty-two down-regulated. Using the criteria for fold change (fc) , 0·833 or . 1·2 and P,0·05, the most affected (down-regulated) signalling pathways were hedgehog, chemokine and leucocyte transendothelial migration pathways. ACE expression was also slightly decreased (fc 0·86; P¼ 0·047). In conclusion, long-term treatment with fermented milk enriched with tripeptides and plant sterols decreases SBP, improves endothelial dysfunction and affects signalling pathways related to inflammatory responses in SHR.Key words: Milk-derived bioactive peptides: Experimental hypertension: Spontaneously hypertensive rats: Plant sterols: Endothelial function Hypertension is one of the most important risk factors for CHD, heart failure, cerebrovascular disease and chronic kidney disease. The prevalence of hypertension is increasing worldwide, both in developed and developing countries (1) . Up to 30 % of the world's adult population was estimated to have hypertension in 2000 (2) . Any reductions in blood pressure, however small, are meaningful; a systolic blood pressure (SBP) reduction of 9 mmHg and a diastolic blood pressure reduction of 5 mmHg reduce the risk of stroke by [35][36][37][38][39][40] .Besides pharmacological therapy, lifestyle and nutritional factors play a significant role in the prevention and treatment of hypertension and related disorders. Low saturated fat and Na intake and increased consumption of K, Ca and soluble fibre positively affect blood pressure (4) . Plant sterols and stanols (also called as phytosterols and -stanols) have wellestablished cholesterol-lowering effects. The consumption of 2 g plant sterols per d has been shown to lowe...