Dietary lipid modulation of alpha-adrenoceptor (adrenergic receptor)- and non-adrenoceptor-mediated contractile properties of isolated rat abdominal aortic segments were assessed during the early developmental period. Rats were raised from conception to 90 days of age on semisynthetic diets containing various types and amounts of lipids. Aortic segments from three groups of rats fed high-fat diets (15% wt/wt) consisting of olive oil, corn oil, or lard as the sole lipid sources were compared with those from rats fed a low-fat control diet containing corn oil (5% wt/wt). alpha-Adrenoceptor activities were assessed by measuring the norepinephrine dose response of the tissue rings with and without partial inactivation of alpha-receptors by benextramine. alpha-Adrenoceptor sensitivity to norepinephrine increased, whereas receptor affinity decreased significantly in rats raised on high-fat diets. Qualitative features of dietary lipids influenced non-adrenoceptor-dependent aspects of vascular contractility. Diets rich in polyunsaturated fatty acids (high- and low-fat corn oil) raised the maximum response to norepinephrine and the contractile response to 60 mM potassium compared with more-saturated diets (olive oil and lard). These results demonstrate an effect of chronic feeding of high dietary fat on alpha-adrenoceptor-mediated contractility of abdominal aortic rings from young Sprague-Dawley rats. Qualitative features of dietary lipids also appear to modify receptor-independent parameters of the contractile response of the arterial tissue rings in these animals.