Endothelium-dependent vasomotor effects of telmisartan in isolated rat femoral arteries

AT₁ receptor antagonists (ARBs) are drugs widely used for preventing and/or treating major cardiovascular diseases. Some of these drugs also show AT₁ receptor-independent effects that may have patho-physiological significance, such as Peroxisome Proliferator-Activated Receptors gamma (PPARγ) stimulation. Here we investigated the effect of telmisartan (that also stimulates PPARγ) on vasomotor responses of femoral arteries isolated from rat, in comparison to losartan. Femoral artery segments were mounted in a wire myograph and challenged with cumulative concentrations of phenylephrine (PE) and acetylcholine (ACh) after 30-min incubation in the absence or presence of 30 μM telmisartan or 30 μM losartan. Vasomotor responses were not significantly changed by losartan, whereas telmisartan reduced vasoconstriction to PE and increased vasodilatation to ACh. Incubation with 0.1 mM N^G-nitro-l-arginine abolished relaxation to ACh in untreated controls as well as in losartan-treated preparations, but did not in telmisartan-treated preparations (were 20% relaxation subsisted); this residual relaxing effect was abolished by indomethacin and by endothelium removal. Incubation with 30 μM GW9662 (PPARγ antagonist), 10 μM PD123319 (AT₂ antagonist) or 30 μM A779 (angiotensin(1-7)/Mas antagonist) did not change the effect of telmisartan on vasomotor responses in preparations with intact endothelium. We conclude that telmisartan modifies constriction and dilatation of isolated arteries in an endothelium-dependent manner, involving both nitric oxide and prostanoid production. The present effect of telmisartan, however, does not seem to involve PPARγ, AT₂ or angiotensin(1-7)/Mas.