26
Ν. G. PON
Niemi and Ikonen showed that among other oxidative enzymes present
in the Leydig cells of rat testis is glucose-6-phosphate dehydrogenase
(185). These cells, which are the producer of testosterone, contain less
of this dehydrogenase after hypophysectomy of the rat. These workers
were also unable to demonstrate any in vivo effect of the above-mentioned pituitary hormones on the hexose monophosphate shunt.
There was no evidence of the pentose-shunt activity in ram, bull,
dog, or fowl spermatozoa as measured by incubating them with variously
labeled glucose (186). In all these cases the C-l:C-6 ratios were close to
unity. Sperm cells from different locations, however, seem to use different
metabolic routes for oxidizing glucose. Thus, ram and bull epididymal
spermatozoa oxidize glucose-l-C
14 and glucose-6-C
14 to yield C0 2 with
a C-l:C-6 ratio of about 1, whereas testicular sperm cells gave a ratio
which indicated preferential oxidation of C-l (187). The ratio of TPN
4
to DPN
+ may be the controlling factor in this case.
7. Erythrocytes, Genetically Determined
Glucose-6-phosphate
Dehydrogenase Deficiency and Leukocytes
Rather than cope with the already enormous mass of literature dealing with the pentose phosphate cycle in erythrocytes, this reviewer
recommends to the reader recent and more complete coverage of this
subject by Schweiger (188). For the sake of convenience, however, some
highlights are reported here.
Apparently, the often cited experiments of Barron and Harrop started
the whole line of investigation on the alternate pathway of carbohydrate
metabolism in erythrocytes (23) when they showed that methylene blue
stimulates oxygen uptake of rabbit erythrocytes twentyfold. With the
discovery of glucose-6-phosphate dehydrogenase in erythrocytes by Warburg and Christian (21), the concept of a new route of glucose metabolism became well entrenched. Since those historic times, many studies
have been carried out on erythrocytes from all sources using mainly three
methods: measuring C
14 0 2 production from labeled glucose, assaying
enzymes, and determining the pattern of products formed from various
substrates.
Examples of studies using labeled glucose in erythrocytes are described below: Brin and Yonemoto studied the effect of methylene blue
on C0 2 production and 0 2 consumption by human erythrocytes (189).
Murphy used uniformly labeled glucose to evaluate the relative contribution of the pentose phosphate pathway in glucose metabolism
(190).
Redding and Johnson investigated the effect of the state of the thyroid
on glucose metabolism by blood (191). Strömme and Eldjarn determined
Ν. G. PON
Niemi and Ikonen showed that among other oxidative enzymes present
in the Leydig cells of rat testis is glucose-6-phosphate dehydrogenase
(185). These cells, which are the producer of testosterone, contain less
of this dehydrogenase after hypophysectomy of the rat. These workers
were also unable to demonstrate any in vivo effect of the above-mentioned pituitary hormones on the hexose monophosphate shunt.
There was no evidence of the pentose-shunt activity in ram, bull,
dog, or fowl spermatozoa as measured by incubating them with variously
labeled glucose (186). In all these cases the C-l:C-6 ratios were close to
unity. Sperm cells from different locations, however, seem to use different
metabolic routes for oxidizing glucose. Thus, ram and bull epididymal
spermatozoa oxidize glucose-l-C
14 and glucose-6-C
14 to yield C0 2 with
a C-l:C-6 ratio of about 1, whereas testicular sperm cells gave a ratio
which indicated preferential oxidation of C-l (187). The ratio of TPN
4
to DPN
+ may be the controlling factor in this case.
7. Erythrocytes, Genetically Determined
Glucose-6-phosphate
Dehydrogenase Deficiency and Leukocytes
Rather than cope with the already enormous mass of literature dealing with the pentose phosphate cycle in erythrocytes, this reviewer
recommends to the reader recent and more complete coverage of this
subject by Schweiger (188). For the sake of convenience, however, some
highlights are reported here.
Apparently, the often cited experiments of Barron and Harrop started
the whole line of investigation on the alternate pathway of carbohydrate
metabolism in erythrocytes (23) when they showed that methylene blue
stimulates oxygen uptake of rabbit erythrocytes twentyfold. With the
discovery of glucose-6-phosphate dehydrogenase in erythrocytes by Warburg and Christian (21), the concept of a new route of glucose metabolism became well entrenched. Since those historic times, many studies
have been carried out on erythrocytes from all sources using mainly three
methods: measuring C
14 0 2 production from labeled glucose, assaying
enzymes, and determining the pattern of products formed from various
substrates.
Examples of studies using labeled glucose in erythrocytes are described below: Brin and Yonemoto studied the effect of methylene blue
on C0 2 production and 0 2 consumption by human erythrocytes (189).
Murphy used uniformly labeled glucose to evaluate the relative contribution of the pentose phosphate pathway in glucose metabolism
(190).
Redding and Johnson investigated the effect of the state of the thyroid
on glucose metabolism by blood (191). Strömme and Eldjarn determined