Characterization of endothelium-derived hyperpolarizing factor in the human forearm microcirculation

Area of Science:

• Cardiovascular Physiology
• Human Microcirculation Research
• Vascular Endothelium Function

Background:

• The precise identity of endothelium-dependent hyperpolarizing factor (EDHF) in human circulation remains a subject of debate.
• Understanding EDHF's role is crucial for comprehending endothelium-dependent vasomotion and potential therapeutic targets.

Purpose of the Study:

• To investigate the contribution of EDHF to endothelium-dependent vasomotion in the human forearm microvasculature.
• To explore the effects of potassium (K+) and miconazole, a cytochrome P-450 inhibitor, on bradykinin-induced vasodilation.

Main Methods:

• Healthy human subjects received intra-arterial infusions of study drugs.
• Forearm blood flow was measured using strain-gauge plethysmography.
• Responses to bradykinin and sodium nitroprusside were assessed under various conditions, including high K+ and after inhibition of nitric oxide and prostaglandin pathways.

Main Results:

• High K+ concentrations significantly inhibited the vasodilator response to bradykinin but not to sodium nitroprusside.
• Miconazole suppressed bradykinin-mediated vasodilation only after nitric oxide synthase and cyclooxygenase inhibition.
• These findings indicate a role for EDHF in nitric oxide- and prostaglandin-independent vasodilation.

Conclusions:

• EDHF contributes to endothelium-dependent vasomotion in the human forearm microvasculature.
• The results suggest that EDHF is likely a cytochrome P-450 derivative, potentially an epoxyeicosatrienoic acid.