42
Ν. G. PON
one-half and the latter to three-fourths those of the control animals maintained at 26 ± 1°C. (305). They attribute the discrepancy between the
C-l:C-6 results and theirs to the much longer exposure of the animals
to cold intervals, which perhaps may profoundly influence the tissue
TABLE V
EFFECT OF DIETARY CONDITIONS ON THE G-6-P DH AND/OR 6-PG DH
ACTIVITIES IN THE RAT LIVER
Dietary conditions
Control diet
Effect on enzymatic activity Reference
Choline-deficient (fatNormal diet;
G-6-P DH: Initially above,
(295)
free) diet
i.e., ad
then below control
libitum
Corn diet
15% casein diet G-6-P DH and 6-PG DH:
(301)
below control
Corn diet + lysine
15% casein diet G-6-P DH and 6-PG DH:
(301)
and/or tryptophan
above corn diet, but still
below control
Low-casein diet, minus
15% casein diet G-6-P DH and 6-PG DH:
(301)
threonine
below control
Low-casein diet, plus
15% casein diet G-6-P DH and 6-PG DH:
(301)
threonine
above control, former to
greater extent than latter
Fasted 48 hr., refed high- Normal diet
G-6-P DH and 6-PG DH:
(298)
carbohydrate, low-fat
markedly above control and
diet
increasing with refeeding
time
High-glucose diet
Normal diet
G-6-P DH and 6-PG DH:
(302)
above control
High-fructose diet
Normal diet
G-6-P DH and 6-PG DH:
(302)
above control
Fasted 6 days, refed 1
Fasted 6 days G-6-P DH and 6-PG DH:
(303)
day
above control
Fasted 6 days, refed 1
Fasted 6 days G-6-P DH: above control
(303)
day -f- ethionine
6-PG DH: same as control
Scorbutogenic diet
0
Scorbutogenic G-6-P DH and 6-PG DH:
(283)
diet plus
above control
ascorbate
β Guinea pigs were used as experimental animals in this case.
metabolic rates. Since the cold-exposed rats have a depressed capacity
for TPNH production, owing to the reduced activity of the dehydrogenases, then the decreased fatty acid synthesis observed may be
ascribed to the decreased level of these enzymes. The reason for the
reduced dehydrogenases activities is unknown, but the decrease is not
due to hyperthyroidism in the cold, since this condition is known to
lead to enhanced G-6-P DH and 6-PG DH activities.
Ν. G. PON
one-half and the latter to three-fourths those of the control animals maintained at 26 ± 1°C. (305). They attribute the discrepancy between the
C-l:C-6 results and theirs to the much longer exposure of the animals
to cold intervals, which perhaps may profoundly influence the tissue
TABLE V
EFFECT OF DIETARY CONDITIONS ON THE G-6-P DH AND/OR 6-PG DH
ACTIVITIES IN THE RAT LIVER
Dietary conditions
Control diet
Effect on enzymatic activity Reference
Choline-deficient (fatNormal diet;
G-6-P DH: Initially above,
(295)
free) diet
i.e., ad
then below control
libitum
Corn diet
15% casein diet G-6-P DH and 6-PG DH:
(301)
below control
Corn diet + lysine
15% casein diet G-6-P DH and 6-PG DH:
(301)
and/or tryptophan
above corn diet, but still
below control
Low-casein diet, minus
15% casein diet G-6-P DH and 6-PG DH:
(301)
threonine
below control
Low-casein diet, plus
15% casein diet G-6-P DH and 6-PG DH:
(301)
threonine
above control, former to
greater extent than latter
Fasted 48 hr., refed high- Normal diet
G-6-P DH and 6-PG DH:
(298)
carbohydrate, low-fat
markedly above control and
diet
increasing with refeeding
time
High-glucose diet
Normal diet
G-6-P DH and 6-PG DH:
(302)
above control
High-fructose diet
Normal diet
G-6-P DH and 6-PG DH:
(302)
above control
Fasted 6 days, refed 1
Fasted 6 days G-6-P DH and 6-PG DH:
(303)
day
above control
Fasted 6 days, refed 1
Fasted 6 days G-6-P DH: above control
(303)
day -f- ethionine
6-PG DH: same as control
Scorbutogenic diet
0
Scorbutogenic G-6-P DH and 6-PG DH:
(283)
diet plus
above control
ascorbate
β Guinea pigs were used as experimental animals in this case.
metabolic rates. Since the cold-exposed rats have a depressed capacity
for TPNH production, owing to the reduced activity of the dehydrogenases, then the decreased fatty acid synthesis observed may be
ascribed to the decreased level of these enzymes. The reason for the
reduced dehydrogenases activities is unknown, but the decrease is not
due to hyperthyroidism in the cold, since this condition is known to
lead to enhanced G-6-P DH and 6-PG DH activities.