Serum adenosine deaminase activity in HIV positive subjects. A hypothesis on the significance of ADA2

Adenosine deaminase activity (ADA) was assayed in the serum of 137 HIV positive subjects: 131 intravenous drug abusers, 3 female partners of HIV positive abusers, 1 son of HIV positive abuser and 2 blood-transfused patients, subdivided into the following groups: 73 asymptomatic, 15 with ARC, 37 with LAS, 5 with L-AIDS and 7 with AIDS. Results show an increase of ADA activity in 100% of L-AIDS group, in 64% of AIDS group, in 62% and 42% of LAS and ARC groups, respectively, and in 36% of the asymptomatic groups. These findings must be confirmed with wider series in order to be further and better evaluated. According to relative substrate specificities, optimal pH and Km, enzymatic activity can be attributed principally to the ADA2 isoenzyme. The probability that ADA2 originates exclusively from the Monocyte-Macrophage cell system (MoMaCS) which actively releases this enzyme in the presence of live parasites in the cells' interior, is discussed. Moreover, it was hypothesized that in the MoMaCS the enzyme constitutes a microbicidal mechanism independent of the respiratory burst.

Increased red cell calcium, decreased calcium adenosine triphosphatase, and altered membrane proteins during fava bean hemolysis in glucose-6-phosphate dehydrogenase-deficient (Mediterranean variant) individuals

RBCs from four glucose-6-phosphate dehydrogenase (G6PD)-deficient (Mediterranean variant) subjects were studied during fava bean hemolysis. In the density-fractionated RBC calcium level, Ca2+-ATPase activity, reduced glutathione level, and ghost protein pattern were studied. In the bottom fraction, containing most heavily damaged RBCs, calcium level ranged from 143 to 244 mumol/L RBCs (healthy G6PD-deficient controls: 17 +/- 5 mumol/L RBCs). The Ca2+-ATPase activity ranged from 0.87 to 1.84 mumol ATP consumed/g Hb/min (healthy G6PD-deficient controls: 2.27 +/- 0.4). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of ghosts showed: (1) the presence of high mol wt aggregates (in three cases they were reduced by dithioerythritol; in one case, only partial reduction was possible); (2) the presence of multiple, scattered new bands; and (3) the reduction of band 3. Oxidant-mediated damage to active calcium extrusion, hypothetically associated with increased calcium permeability, may explain the large increase in calcium levels. They, in turn, could activate calcium-dependent protease activity, giving rise to the profound changes in the ghost protein pattern.