Effects of hypercholesterolemia on the microsomal membrane fluidity of intimal-medial versus medial layers of swine aorta: Implications for the pathogenesis of vasospasm

Abstract

The hypothesis was examined that hypercholesterolemia induces a decrease in arterial microsomal membrane fluidity. To investigate this hypothesis, the fluorescence anisotropy ( r) of 1,6-diphenylhexa-1,3,5-triene was measured in aortic microsomes isolated from the intimal—medial (IM) and medial (M) layers of swine thoracic aortas. After 10 weeks of feeding a high fat (10% lard) diet, serum cholesterol increased 2.3-fold compared to 3.6-fold in pigs fed a similar diet supplemented with 2% cholesterol. Based upon differences in r, the membrane fluidity of the IM layer was significantly less than the M layers. The membrane fluidity of the IM layer was inversely related to the severity of hypercholesterolemia regardless of dietary treatment. There were no differences in membrane fluidity among the three dissected M layers and the membrane fluidity of these layers was refractory to changes in serum cholesterol. A decrease in the membrane fluidity of the IM layer may contribute to the abnormal regulation of vascular tone which underlies the development of vasospasm in atherosclerotic arteries.