Modulation of guanylate cyclase by lipoxygenase inhibitors.

Drugs that inhibit endothelium-dependent relaxation were tested to determine their effect on soluble guanylate cyclase purified from dog aorta. Basal, arachidonic acid (10(-5) M)-stimulated, and nitroprusside (5 X 10(-5) M)-stimulated guanylate cyclase activities were inhibited by methylene blue and the lipoxygenase inhibitors nordihydroguaiaretic acid and eicosatetraynoic acid. The effective inhibitory doses were in the range of those that have been reported to inhibit endothelium-dependent relaxation. Other compounds known to inhibit endothelium-dependent relaxation had little or no effect on guanylate cyclase activity. Basal guanylate cyclase activity was more resistant to inhibition than were activated states of the enzyme. The data suggest that reported inhibition of endothelium-dependent relaxation by some lipoxygenase inhibitors may be the result, at least in part, of their direct effect on guanylate cyclase activity.