Effects of hypertension on hypercholesterolemia-induced changes in contraction of rabbit aorta and carotid artery

Abstract Reactivity of aortic and carotid strips from control; hypertensive; hypercholesterolemic; and hypertensive/hypercholesterolemic rabbits was studied. Maximal stress was less in strips from hypertensive/hypercholesterolemic animals. Norepinephrine sensitivity was increased in the carotid artery from hypertensive/hypercholesterolemic animals (EC 50 : 0.11 μM; 0.35 μM control). CaCl 2 sensitivity during norepinephrine-induced contractions was enhanced by hypertension and hypercholesterolemia (carotid EC 50 : 0.10 mM; 0.38 mM control; aorta EC 50 : 0.12 mM; 0.82 mM control) Similar results were obtained during membrane depolarization. 5-hydroxytryptamine sensitivity (EC 50 : 0.15μM carotid; 0.18 μM aorta) was decreased during hypertension (EC 50 : 0.51 μM carotid; 1.13 μM aorta) and by hypercholesterolemia (EC 50 : 1.76 μM carotid; 1.53 μM aorta). Our results support the hypothesis that hypertension and hypercholesterolemia increase vascular sensitivity by increasing Ca 2+ permeability. Our results also suggest that hypertension and hypercholesterolemia selectively decrease 5-hydroxytryptamine-induced contractions.