Protective action of elastase on changes in mechanical properties of vascular smooth muscles during...

Effects of oral administration of elastase on changes in contractile responses of smooth muscle cells of the aorta and pulmonary artery were studied in rabbits fed a high-cholesterol diet. In rabbits on high-cholesterol diet, the acetylcholine (ACh)-induced endothelium-dependent relaxation was gradually decreased, and over 10 weeks on this diet, the relaxing responses were diminished, abolished or converted to contraction, while contractions produced by high-potassium (high-K) were enhanced and those produced by noradrenaline (NA) were decreased in sensitivity. In tissues from aged rabbits (2-8 years old), the ACh-induced relaxation was decreased while sensitivity to NA or high-K was elevated, in comparison with findings in young rabbits (3-4 months old). Oral administration of elastase together with high-cholesterol diet inhibited decreases in the ACh-induced relaxation or the NA-contraction, but not the increase in high-K contraction. The elevated concentrations of cholesterol but not those of triglycerides in sera, were significantly lowered by elastase. These results provide evidence that elastase has a hypocholesterolemic action and a protective role in atherosclerosis.