Dr. Wallace et R. Dawson, ASSESSMENT OF REGIONAL PHOSPHATE-ACTIVATED GLUTAMINASE (PAG) ACTIVITYAND KINETICS IN ADULT AND AGED FISCHER-344 RATS, Age, 17(2), 1994, pp. 59-63
The regional activity of phosphate-activated glutaminase (PAG) was ass
essed in 8-month-old and 28-month-old male Fischer-344 (F344) rats fro
m the temporal cortex (TCX), striatum (STR) and hippocampus (HIPP). Ba
sal activity, as represented by activity in the presence of 10 mM phos
phate, was decreased 23% in the TCX from aged rats compared to adults
while neither the STR or HIPP exhibited age-related changes. In the pr
esence of 100 mM phosphate, which will maximally stimulate PAG activit
y, none of the regions displayed age-related changes although all grou
ps showed increased PAG activity of 112-169% compared to corresponding
values in the presence of 10 mM phosphate. Kinetic analysis revealed
no alterations in the apparent affinity (Km) of PAG for glutamine in t
he TCX and STR, but the Km value was increased 32% in the HIPP(255+/-1
2 muM compared to 336+/-22 muM). There were no significant changes in
Vmax values. Regional variability seen in PAG basal activity and kinet
ics may reflect regional differences in glutamatergic innervation or g
lutamate-specific metabolic requirements of these three regions. These
possibilities are discussed with regard to the aging process and neur
al degeneration which may occur as a result of a dysfunctional glutama
tergic system.