title: Effects of insulin on vascular responses to mental stress and norepinephrine in human forearm.
abstract: Essential hypertension is frequently associated with insulin resistance and hyperinsulinemia. In vitro, insulin has vasodilator actions, but its possible hemodynamic effect on muscular vascular beds in humans is a matter of controversy. We investigated the effects of local hyperinsulinemia on the vascular responses to norepinephrine and physiological vasodilation during mental stress in the perfused-forearm model. Nine glucose-tolerant, normotensive, nonobese men (aged 22 to 36 years) participated. Forearm perfusion studies (venous occlusion plethysmography) were performed during randomized, double-blind intrabrachial artery infusions of insulin (to raise plasma insulin 100 microU/mL) or placebo for 2 hours. A mental stress test and stepwise intra-arterial infusion of norepinephrine (6 to 1200 ng/min) were performed during each infusion. Insulin infusion increased venous plasma insulin to 98.4 microU/mL and increased net glucose uptake threefold. Insulin had a gradual vasodilator effect (P < .05 by ANOVA), and after 90 minutes blood flow was 36 percent units higher relative to the control arm than during placebo (P = .005). During mental stress, forearm blood flow increased by 81% (t test, P = .006) and 92% (P = .01) in the study arm during insulin and placebo infusions, respectively (insulin versus placebo, P = NS). An increased forearm blood flow was maintained throughout the mental stress test during insulin infusion (ANOVA, P = .03). Forearm glucose uptake increased during stress, reflecting forearm hyperperfusion since fractional glucose extraction was unaffected by stress. The increased blood flow was maintained throughout the five norepinephrine dose steps (ANOVA, P < .04).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Clinical Physiology, Ostra Hospital, Göteborg University, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Jern
mesh_terms: D001808:Blood Vessels / Q000187:drug effects; D004311:Double-Blind Method; D005542:Forearm / Q000098:blood supply*; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D006946:Hyperinsulinism / Q000503:physiopathology; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology*; D010919:Placebos; D012039:Regional Blood Flow / Q000187:drug effects; D013315:Stress, Psychological / Q000503:physiopathology*
chemical_list: D007328:Insulin; D010919:Placebos; D009638:Norepinephrine