Ethanol modulates cyclic GMP metabolism in cultured coronary smooth muscle cells

The authors tested the hypothesis that ethanol or its metabolite acetaldehyde might interfere in cyclic guanosine monophosphate (GMP) metabolism in coronary smooth muscle cells. Ethanol at the physiologically relevant concentration of 4.0 mg/mL or more significantly decreased basal guanylate cyclase activity and inhibited activation of the enzyme by sodium nitroprusside (SNP) in cultured porcine coronary smooth muscle cells. Two isoforms of phosphodiesterase (PDE), cyclic GMP-specific form and calmodulin-stimulated form, were both inhibited by 12.0 mg/mL or more ethanol. Intact cell study revealed that although 12.0 mg/mL or more ethanol was needed to significantly decrease cyclic GMP accumulation in control cells, 4.0 mg/mL or more ethanol significantly inhibited the increase of cyclic GMP accumulation induced by 1 microns SNP. Acetaldehyde showed similar effects, but the concentrations involved were more than physiological. Thus, ethanol may decrease cellular cyclic GMP levels and attenuate cyclic GMP accumulation in response to SNP in coronary smooth muscle cells by inhibiting soluble guanylate cyclase activity at physiologically relevant concentrations.