['The present study was designed to examine, using isolated preparations of thoracic aorta, the effects of artificial phosphatidylcholine vesicles (liposomes) on vascular endothelium-dependent responses in spontaneously hypertensive rats (SHR) compared with those in Wistar-Kyoto (WKY) normotensive rats.', 'Phosphatidylcholine liposomes, which possess the ability to repair the plasma membrane of living cells, were used in these experiments.', 'Liposomes were prepared from egg phosphatidylcholine. A suspension of lipid was subjected to ultrasound treatment at 20 degrees C at a frequency of 44 kHz for 45 s. The contraction of vascular smooth muscle was recorded using a force-displacement transducer coupled with a physiograph.', 'It was shown that aortic smooth muscle from SHR demonstrated a loss of endothelium-dependent relaxation in acetylcholine (10(-6) mol/l) compared with WKY rat aortic smooth muscle. Liposomes in a concentration of 100-125 micrograms/ml restored these endothelium-dependent responses more effectively than L-arginine (10(-5) to 10(-4) mol/l), which is known to be a precursor of endothelium-derived relaxing factor (EDRF). This effect was not observed in denuded aortic rings, and liposomes lost their ability of repairing endothelium-dependent vascular relaxant responses in the presence of methylene blue (5 x 10(-5) mol/l), which inhibits soluble guanylyl cyclase activation by nitric oxide (NO), and N omega-nitro-L-arginine (L-NNA, 5 x 10(-5) to 10(-4) mol/l), a potent and selective inhibitor of NO synthase.'] Do phospholipid vesicles ( liposomes ) restore endothelium-dependent cholinergic relaxation in thoracic aorta from spontaneously hypertensive rats?