VASCULAR WALL REACTIVITY IN CONDUCTANCE AND RESISTANCE ARTERIES - DIFFERENTIAL-EFFECTS OF INSULIN-RESISTANCE

Insulin resistance is associated with an increased risk of cardiovascu lar disease that is probably related to abnormalities of vascular wall function. The JCR:LA-cp rat is a unique animal model of human vascula r disease that exhibits a profound insulin resistance, vasculopathy, a nd cardiovascular disease, and allows study of the relationships betwe en insulin resistance and vascular function. Conductance and resistanc e arteries serve different functions, thus vascular disease may affect these types of artery differently. Concentration-response curves to n orepinephrine, phenylephrine, and acetylcholine were studied in conduc tance vessels (aortic rings) and resistance vessels (mesenteric arteri es) from 12-week-old male obese and lean SCR:LA-cp rats. The aortic ri ngs and mesenteric arteries from obese rats showed increased maximal r esponse to phenylephrine compared with those from lean rats, whereas o nly the mesenteric arteries from obese rats showed increased maximal r esponse to norepinephrine, In aortic rings, relaxation to acetylcholin e was similar for both genotypes, but the mesenteric arteries of obese rats showed impaired relaxation to acetylcholine. We conclude that th e sensitivity to vasoconstriction is enhanced in aortic rings and mese nteric arteries of obese male JCR:LA-cp rats, but endothelial function is impaired only in the mesenteric resistance arteries of these anima ls. Hence functional aberrations in the obese, insulin-resistant state are more pronounced in mesenteric resistance arteries than in a major conductance artery.