Cicletanine does not act on the kidney alone: it also dilates the vessels. This vasodilation works through several pathways. It stimulates the synthesis, in the vascular wall, of prostaglandins including prostacyclin, a powerful relaxant. It also inhibits the low-Km cyclic GMP phosphodiesterases, which prolongs the relaxation signal, and it blocks calcium channels, which reduces smooth muscle contraction.
Experimental work refines this picture. On the rat aorta, cicletanine produces an endothelium-dependent relaxation via the cyclo-oxygenase pathway (prostacyclin) and the NO synthase pathway, and an endothelium-independent relaxation through the opening of potassium channels at higher concentration. In another model, that of liver sinusoidal endothelial cells, it increases the phosphorylation of eNOS on serine 1177 and the production of nitric oxide, through the Akt and MAP kinase/Erk signaling pathways. In the DOCA-salt hypertensive rat, its antihypertensive effect is linked to a rise in prostacyclin and a fall in sympathetic tone, and pretreatment with indomethacin, which blocks prostaglandin synthesis, attenuates its acute blood-pressure-lowering effect.