| Abstract: | Summary. The vibrating reed electrometer and ionization chamber have been adapted for the instantaneous and continuous measurement of pentose phosphate pathway (PPP) activity in human red cells. PPP activity was determined by measuring the conversion of glucose-1-14C to 14CO2. PPP activity was independent of ambient glucose concentration over the range of 50–500 mg % and was stimulated up to 36-, 18- and 6-fold by methylene blue, ascorbic acid and primaquine, respectively. PPP activity was increased 24% and 41% when incubation temperatures were raised to 39°C and 40.5°C, respectively. PPP activity in unstimulated RBC was twice as great in 95% O2 as in 20% O2 and in 10% O2 was only slightly less than in 20% O2. The PPP activity was found to be very pH-dependent. PPP activity in plasma was about twice as great as in Krebs-Ringer bicarbonate buffer. Thus, the activity of the PPP in red cells is altered significantly in vitro by incubation conditions designed to mimic various clinical states. |
