ACE and essential hypertension: Similar results revealing no association between ACE I/D genotype and essential hypertension were also reported on Tibetan highlanders [2, 35], USA Caucasians [36], Japanese lowlanders [37], Dutch population [38], and other low-altitude populations [39], which probably suggests that mutations at the ACE locus do not commonly contribute to the pathogenesis of hypertension in the populations mentioned above [39].