CA2+ CAM-SENSITIVE ADENYLYL-CYCLASE ACTIVITY IS DECREASED IN THE ALZHEIMERS BRAIN - POSSIBLE RELATION TO TYPE-I ADENYLYL-CYCLASE/

Immunoreactivities of four subtypes of adenylyl cyclase (AC) (types I, II, IV and V/VI), and basal, forskolin-and Mn2+-stimulated AC activit ies with or without calcium and calmodulin (Ca2+/CaM) were estimated i n parietal cortex membranes from cases with dementia of the Alzheimer type (DAT) and age-matched controls. Immunoreactivities of AC-I and AC -II were significantly decreased, but those of AC-IV and AC-V/VI did n ot change in DAT brains. There was a significant correlation of AC-I i mmunoreactivity with Ca2+/CaM-sensitive AC activity, but not with the Ca2+/CaM-insensitive activity. Ca2+/CaM-sensitive AC activity was sign ificantly lower in DAT than in the control, indicating that impairment of Ca2+/CaM-sensitive AC-I is clearly involved in the pathophysiology of DAT.