Effects of pioglitazone and rosiglitazone on vascular function of mesenteric resistance arteries in rat genetic hypertension.

Glitazones exhibit beneficial effects in the vascular system, both on large vessels and at a microcirculatory level. We previously reported the effects of glitazones in the aorta of spontaneously hypertensive rats (SHR). We focus now on the acute and long-term actions of these drugs on mesenteric resistance arteries of the SHR. Incubation with pioglitazone or rosiglitazone (10⁻⁵ mol/l) improved endothelium-dependent relaxations to acetylcholine and the endothelial modulation of phenylephrine contractions. Acetylcholine relaxations that were abolished by N(G)-nitro-L-arginine methylester were partly recovered by the glitazones, but no effects of these drugs were observed in the presence of indomethacin or indomethacin + L-NAME. Glitazones did not change the contractions to U46619 or the endothelium-independent relaxation to sodium nitroprusside. Three-week oral pioglitazone or rosiglitazone treatment (3 and 10 mg/kg/day, respectively) confirmed the acute experiments. Thus, in microvessels, glitazones improve endothelial function in such a way that they do not alter endothelial nitric oxide release but reduce the production of vasoconstrictor prostanoids from endothelial cells.