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Endothelium-Derived Hyperpolarizing Factor and Skin Microcirculation

 
Abstract:

This post is also available in: enEnglish slSlovenščina (Slovenian)

The skin microcirculation is controlled by systemic and local factors; the latter are mainly released from the endothelium. One of important endothelial vasodilators is endotheli­um-derived hyperpolarizing factor (EDHF) whose function can be assessed by blocking other vasodilators, such as nitric oxide (NO) and prostacyclin (PGI2). The role and nature of EDHF in humans remains to be elucidated. The aim of our study was therefore to investigate and characterize the NO- and PGI2-independent mechanism, potentially attributable to EDHF, in human skin microcirculation. 14 healthy male volunteers (aged 20 to 37 years, mean age ± 1.7) were included in the study. Cutaneous blood flow was measured using the laser Doppler (LD) method on the volar aspect of the forearm and expressed in perfusion units (PU). Endothelial nitric oxide synthase (eNOS) and cyclooxygenase (COX) were inhibited by subcutaneously injecting Nm-monomethyl L-arginine (L-NMMA) and diclofenac, respectively. The potential involvement of cytochrome P450 (CYP) in the generation of EDHF was eval­uated by injecting the selective CYP 2C9 inhibitor sulfaphenazole. The baseline LD flow and microvascular reactivity were assessed by performing iontophoresis of acetylcholine (ACh, endothelium-dependent vasodilator) and by measuring postocclusive reactive hyperemia (PRH). eNOS and COX inhibition did not affect the baseline LDF (12.5 ±2.3 PU in the treat­ed site and 10.9 ± 1.8 PU in the control site, t-test), but it significantly attenuated ACh-induced vasodilatation in the eNOS and COX-treated site (35.6 ± 5.7 PU in the treated site vs. 66.6 ± 8.3 PU in the control site, t-test, p < 0.05). Nevertheless, about 70% of ACh-induced vasodi­latation persisted. In addition, L-NMMA and diclofenac significantly attenuated the area under the PRH curve, but LDF increase after removal of occlusion was preserved. Sulfaphenazole had no impact either on the baseline LDF or on ACh-induced vasodilatation or PRH para­meters. It was concluded that the NO- and PGI2-independent mechanism, potentially attributable to EDHF, plays an important role in the regulation of vascular tone in the human cutaneous microcirculation and that it is probably not a CYP-derived metabolite

Authors:
Lenasi Helena

Keywords:
skin - blood supply, microcirculation, laser - Doppler flowmetry, endothelium vascular, vasodilatation

Cite as:
Med Razgl. 2008; 48: 13–29.
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