Lipid-lowering and skin vascular responses in patients with hypercholesterolaemia and peripheral arterial obstructive disease.

Elevated blood cholesterol is a major risk factor for atherosclerosis. Recent studies show that lowering cholesterol reduces the risk of vascular disease, but the precise mechanisms for vascular improvement are not fully understood. Furthermore, it is not known whether the beneficial effects of cholesterol lowering extend to the skin microvasculature. In this unrandomized, open design study, we used iontophoresis and laser Doppler flowmetry to examine forearm skin perfusion in hypercholesterolaemic patients with PAOD before and after cholesterol-lowering therapy with fluvastatin. Endothelium-dependent and -independent vasodilatation were measured following skin iontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP), respectively. Before cholesterol-lowering, vascular responses to ACh and SNP were reduced significantly in patients compared with responses in control subjects (p < 0.001 and p < 0.05, ANOVA, respectively). Fluvastatin therapy (40 mg/day) for 24 weeks significantly reduced total cholesterol (7.3+/-0.3 to 6.0+/-0.2 mmol/l, p < 0.001) and LDL cholesterol (5.4+/-0.5 to 4.2+/-0.4 mmol/l, p < 0.01). Vasodilatation to SNP was significantly improved at week 24 (p < 0.05). In patients with hypercholesterolaemia and PAOD, cholesterol-lowering with statin therapy significantly improved endothelium-independent vascular responses to SNP in skin microvessels. The application of the non-invasive techniques of iontophoresis and laser Doppler flowmetry may provide useful markers for the assessment of microvascular function in this group of patients.

Oral L-arginine supplementation and cutaneous vascular responses in patients with primary Raynaud's phenomenon.

OBJECTIVE: To assess the effects of oral L-arginine supplementation on cutaneous vascular responses in patients with primary Raynaud's phenomenon (RP). METHODS: Double-blind, crossover comparison of placebo versus L-arginine (8 gm/day for 28 days). Cutaneous vascular responses in the fingers were assessed during iontophoresis of acetylcholine and sodium nitroprusside, which are endothelium-dependent and endothelium-independent vasodilators. RESULTS: In comparison with control subjects, patients with primary RP had diminished endothelium-dependent and -independent vasodilatation (P < 0.05, and P < 0.005, respectively, by analysis of variance). At the 3 doses used, vascular responses to acetylcholine were reduced by 71%, 64%, and 63%, respectively, and responses to sodium nitroprusside were reduced by 67%, 73%, and 66%, respectively. L-arginine had no significant effect on cutaneous vascular responses to acetylcholine or sodium nitroprusside in control subjects or patients with primary RP. CONCLUSION: Reduced vasodilator ability in primary RP is unlikely to be due to an impairment in the L-arginine/nitric oxide pathway.

Cutaneous vascular responses to acetylcholine are mediated by a prostanoid-dependent mechanism in man.

Approximately 50% of the forearm vasodilatation to intra-arterial infusions of acetylcholine is mediated by endothelium-derived nitric oxide. These conclusions have been derived from venous occlusion plethysmographic measurements of total forearm blood flow during co-infusions of acetylcholine and NG-monomethyl-L-arginine (L-NMMA), an inhibitor of nitric oxide synthase. Since venous occlusion plethysmography measures total limb blood flow, the relative proportion of the measurement from skin cannot be determined precisely. To determine the effects of acetylcholine on skin specifically, we have used laser Doppler flowmetry to measure vascular responses to local iontophoresis of acetylcholine in the forearm of normal male volunteers. To elucidate the possible mechanisms of cutaneous vasodilatation to acetylcholine, vascular responses were measured before and after systemic inhibition of prostanoid production and nitric oxide synthesis by oral aspirin (600 mg daily for 3 days) and intravenous L-NMMA (3 mg/kg for 60 min), respectively. After aspirin administration, dose-dependent vascular responses to acetylcholine were reduced significantly by approximately 53% (p < 0.005, ANOVA). In contrast, intravenous L-NMMA appeared to have no significant effect on cutaneous vascular responses to acetylcholine. While the role of nitric oxide is uncertain, vasodilatation to acetylcholine in the forearm skin is mediated largely by a prostanoid-dependent mechanism. Assessment of cutaneous vascular responses to iontophoresis of acetylcholine may, therefore, be useful in diseases where abnormal endothelium-dependent prostanoid function has been implicated.