| Abstract: | Length-tension relationships and contractile responses to agonists associated with cyclic nucleotide levels in aortas from atherosclerotic rabbits were studied. The same number of tissues from healthy rabbits was also studied. Diffuse lesions were produced by denudation of the vascular endothelium of rabbit aorta using a balloon catheter and then feeding these rabbits a high cholesterol diet for two months. Stretch-passive tension curves and length-active tension curves which developed in the presence of 60 mM KCl significantly shifted to the left. The altered length-tension relationships indicate a decreased distensibility in these strips and this is attributed to an enhanced accumulation of collagen. Dose-response curve analysis revealed a marked hypersensitivity to serotonin as indicated by greater pD2 values (negative logarithm of half maximum dose) than seen in the controls. In addition, the mean absolute values of the maximum contraction induced by serotonin and KCl were significantly higher than in the controls. Although cyclic AMP levels in the strips with a pathology were lower and cyclic GMP/cyclic AMP ratios were higher than the controls in the basal state, serotonin induced no marked alterations in the cyclic nucleotides levels in the strips from either the diseased or control rabbits. These mechanical and pharmacological alterations of atherosclerotic vessels may relate to clinical events such as coronary spasm. |
