Ascorbate and dehydroascorbate modulate nitric oxide-induced vasodilations of rat coronary arteries

Area of Science:

• Biochemistry
• Cardiovascular Physiology
• Pharmacology

Background:

• Soluble guanylyl cyclase (GC) is a key heme protein and primary target of nitric oxide (NO).
• The NO/cGMP pathway regulates vascular tone and is crucial for cardiovascular function.
• Understanding modulators of NO sensitivity is vital for cardiovascular health research.

Purpose of the Study:

• To investigate the effects of redox agents, specifically ascorbate (ASC) and dehydroascorbate (DHAA), on NO-induced vasodilation.
• To determine if ASC and DHAA influence the sensitivity of isolated rat coronary arteries to NO.
• To explore the mechanism by which ASC and DHAA might affect the NO/cGMP pathway.

Main Methods:

• Isolated rat coronary arteries were used to measure NO-induced vasodilation.
• NO concentrations were determined using a NO-sensitive electrode.
• Potency of NO was assessed by pEC50 values in the presence and absence of ASC and DHAA.
• Effects on cyclic guanosine monophosphate (cGMP) degradation and potency were tested using analogs and inhibitors.
• Vasodilations induced by non-NO agents (diltiazem, forskolin) were also examined.

Main Results:

• NO induced vasodilation with a pEC50 of 8.24.
• Ascorbate (ASC) significantly enhanced NO potency (pEC50 = 8.70), while dehydroascorbate (DHAA) diminished it (pEC50 = 7.91).
• ASC and DHAA did not affect cGMP degradation or potency, nor vasodilation from diltiazem or forskolin.
• ASC and DHAA modulated NO potency in human mesenteric arteries.
• Other tested redox agents did not affect NO potency.

Conclusions:

• ASC and DHAA modulate arterial sensitivity to NO, likely by affecting the redox state of soluble guanylyl cyclase (GC).
• This modulation occurs independently of effects on cGMP degradation or potency.
• The findings suggest that the redox state of GC is an additional regulatory site within the NO/cGMP pathway.
• These redox agents may play a role in regulating vascular function through the NO signaling pathway.