Huntington's chorea: selective depletion of activity of angiotensin coverting enzyme in the corpus striatum.

The activity of angiotensin converting enzyme, which transforms the relatively inactive decapeptide angiotensin I to the active octapeptide angiotensin II by removal of an L-histidyl-L-leucine residue, has been assayed in numerous region of the calf brain and of the brains of humans with Huntington's chorea and controls. In calf brain there are pronounced regional variations in enzyme activity, with highest activity in the globus pallidus and area postrema. In human brain, enzyme activity is highest in the corpus striatum, with similar levels in the caudate, putamen, and globus pallidus. Converting enzyme activity is reduced by 83 to 92% in the globus pallidus in Huntington's chorea. The caudate and putamen of choreic patients display 62 to 69% reductions in enzyme activity. Converting enzyme activity in two cerebral cortical regions from choreic brains is not significantly different from control.