<prompt> Most potent vasoconstrictor of the pulmonary aery is:EndothelinHypoxiaAngiotensinTXA2  <response>: Endothelin, urotensin, angiotensin are the potent constrictors of the systemic vessels. In case of the pulmonary vessels, hypoxia is the strongest vasoconstrictor, acting the O2-sensitive K channels in the pulmonary vascular smooth muscle cells VSMCs. 