A non-competitive inhibitor of guanylyl and adenylyl cyclases; suppresses STa-, guanylin-, atrial natriuretic peptide-, and C-type natriuretic peptide-induced cGMP accumulation in cells (IC50s = 3.4-11.2 μM); inhibits STa-, forskolin-, cholera toxin-, and isoproterenol-induced chloride efflux in T84 cells; suppresses STa-induced liquid secretion in a rabbit intestinal loop model of toxin-induced secretory diarrhea (10 or 50 μM) ,