Oxýt Hoá
Bất Bình Thường Chất Formaldehyde (gắn với đồng vị phóng xạ Carbon-14)
ấp với Hồng Huyết Cầu Bệnh Nhân Ghiền Rượu và Người bình thường sau khi
uống rượu
Abnormal Oxidation of Formaldehyde incubated with Erythrocytes of
Alcoholics and nonalcoholics after Consumption of Alcoholic Beverages
Ngo Manh Tran, Marcel
Laplante and Etienne LeBel
J. Nuclear Medicine, 13: 677-680,
1972
Abstract: We observed the oxidation of
formaldehyde to CO2 in fresh human erythrocytes. The fact that 14CO2 production
from 14C-formaldehyde occurred in fresh erythrocytes but not in boiled
erythrocytes suggests the presence of enzyme process involved in the oxidation
of this substrate in this human tissue. Similar results were reported
with another monocarbon fragment, i.e, formate, in rats (1) and human
(2) erythrocytes.
In the next series of studies, we observed a decreased 14CO2 production
from 14C-formaldehyde in erythrocytes of alcoholics and nonalcoholics
0-12 hr (p≤0.05) after consumption of alcoholic beverages. This altered
catabolism of formaldehyde may not be due to a delayed physical transport
of this substrate across the cell membrane since no changes in uptakes
of formaldehyde by erythrocytes of normal were found when these cells
were incubated with ethanol (p≥0.05). Therefore the result obtained may
be due to an alteration in erythrocyte metabolism, such as the inhibition
of tetrahydrofolate activity involved in the oxidation of formaldehyde.
Unfortunately, since tetrahydrofolate is extremely labile, little direct
information appears to be available to test the validity of this finding.
There have been reports showing a delay in the oxidation of 14C-formate,
a monocarbon fragment attached to tetrahydrofolate, erythrocytes of folic
acid-deficient rats in vitro, and a decrease in the excretion of 14CO2
after intravenous administration of 14C-formate to folic acid-deficient
rats (3) and patients as well as to irradiated rats in vivo. The latter
result was probably due to an inhibition of tetrahydrofolate by ionizing
radiation (4, 5).
An increased 14CO2 production from 14C-formaldehyde 12-24 hr later (p
≤ 0.05) suggests an over-recovery of enzyme activity. Repeat 14CO2 studies
showed that formaldehyde oxidation returned to the normal when measured
3-21 days after consumption of alcoholic beverages (p ≥ 0.05). These observed
abnormalities in the oxidation of formaldehyde, probably caused by inhibition
of tetrahydrofolate by alcohol, may support the previous result showing
that ethanol suppresses hematopoiesis, perhaps by directly affecting folate
metabolism.
The fact that both inhibition and over-recovery of enzyme activities were
found in very short periods of time may allow an explanation for contradictory
results on serum folate level in alcoholics. Indeed, high mean serum folate
reported by some authors, whereas others have found a low value of this
vitamin level among alcoholics.
The fact that alterations in formaldehyde catabolism occurred in red blood
cells of both alcoholics and nonalcoholics 0-12 hr after consumption of
alcohol but not in these humans 3-21 days later demonstrated the possible
application of this in vitro ionization chamber method with 14C-formaldehyde
to the detection of alcohol in human blood (2).
References:
1) Ngo Manh Tran, Marcel
Laplante and Etienne LeBel: Altered catabolism of 14C-formate by erythrocytes
of folic acid deficient rats: A possible in vitro means for differential
diagnosis of megaloblastic anemias in man? J. Nuclear Medicine, 12:
222-226, 1971.
2) Ngo Manh Tran and Etienne
LeBel: Inhibition of formate and formaldehyde oxidation by ethanol as
an index for estimating alcohol concentration in isolated tissues.
J. Nuclear Medicine 15: 284-87, 1974.
3) Ngo Manh Tran: Quantitation
of certain alterations in intermediary metabolism in vivo associated with
changes in body content of Vitamin B1, B6, B12, and Folic acid using 14CO2
breath analysis. Ph.D. thesis, University of California, Berkeley, California,
1969.
4) Ngo Manh Tran and Saul
Winchell: Effects of ionization radiation on the in vivo metabolism of
monocarbon fragment precursors to CO2. In Frontier of Nuclear Medicine
Book, Horst W., ed, Berlin, Heidelberg, New York, Springer-Verlag, pp
116-127, 1971.
5)
Ngo Manh Tran, Saul Winchell and Steve Landaw: Altered in vivo metabolism
of histidine (imidazole-2-14C) in irradiated rats. Radiation Research,
34: 390-395, 1968.
TAGS: Formaldehyde, oxidation of formaldehyde in erythrocytes, effect
of alcohol on formaldehyde oxidation in erythrocytes, Ngo manh Tran
