3. LIPIDS: STEROID METABOLISM
195
that in the cow the principal ovarian estrogenic hormone is estradiolΠβ and that this is converted to the urinary steroid estradiol-17o: outside the ovary (156). A satisfactory solution to these problems will be
obtained only when reliable methods for the determination of estrogenic
steroids in blood have been developed and applied to a comparison
of the concentrations of these steroids in blood draining from the
estrogen-secreting endocrine glands and in the peripheral circulation.
It has already been pointed out (Section I,B,3,fo) that there is no
satisfactory evidence for the occurrence of estriol in species other than
man, and knowledge of the metabolic relationships of the C-16 oxygensubstituted steroids is restricted to man (157).
2. Excretion of Steroid Metabolites
The products of steroid metabolism have been found in the urine
of various species of animals in conjugation with sulfuric and glucuronic
acids and possibly other substances. No evidence for differences in mode
of conjugation in different species has appeared. Methods for the hydrolysis of conjugates and for the determination of steroids released have
been worked out for urines from human subjects, but it is well known
that these methods are not always applicable to animal urines, and the
quantitative aspects of the study of urinary steroids in animals has
suffered accordingly.
Investigations with steroids labeled with radioactive isotopes have
drawn attention to the importance of the bile and feces as routes for
the excretion of metabolites. In some species these may be the most
important routes. For example 65% of the radioactivity of cortisone
administered intramuscularly to rats appeared in the feces (158) and
similar results were obtained with labeled progesterone (159) and
testosterone (160). In the case of human subjects the greater part of
the radioactivity appeared in the urine (159).
3. Steroid Hormone Metabolism in Domestic Animah
The study of steroid hormone metabolism in domestic animals is of
obvious importance in animal husbandry, and as in the case of man the
investigation of urinary metabolites can provide much valuable information. However, whereas urinary steroids have been thoroughly investigated in man and much emphasis has been placed on the development of reliable methods for the measurement of these steroids, comparatively little work has been done along the same lines with domestic
animals.
From a review of existing knowledge (162) it would appear that
different species show quite different excretory patterns (Table IV). The
195
that in the cow the principal ovarian estrogenic hormone is estradiolΠβ and that this is converted to the urinary steroid estradiol-17o: outside the ovary (156). A satisfactory solution to these problems will be
obtained only when reliable methods for the determination of estrogenic
steroids in blood have been developed and applied to a comparison
of the concentrations of these steroids in blood draining from the
estrogen-secreting endocrine glands and in the peripheral circulation.
It has already been pointed out (Section I,B,3,fo) that there is no
satisfactory evidence for the occurrence of estriol in species other than
man, and knowledge of the metabolic relationships of the C-16 oxygensubstituted steroids is restricted to man (157).
2. Excretion of Steroid Metabolites
The products of steroid metabolism have been found in the urine
of various species of animals in conjugation with sulfuric and glucuronic
acids and possibly other substances. No evidence for differences in mode
of conjugation in different species has appeared. Methods for the hydrolysis of conjugates and for the determination of steroids released have
been worked out for urines from human subjects, but it is well known
that these methods are not always applicable to animal urines, and the
quantitative aspects of the study of urinary steroids in animals has
suffered accordingly.
Investigations with steroids labeled with radioactive isotopes have
drawn attention to the importance of the bile and feces as routes for
the excretion of metabolites. In some species these may be the most
important routes. For example 65% of the radioactivity of cortisone
administered intramuscularly to rats appeared in the feces (158) and
similar results were obtained with labeled progesterone (159) and
testosterone (160). In the case of human subjects the greater part of
the radioactivity appeared in the urine (159).
3. Steroid Hormone Metabolism in Domestic Animah
The study of steroid hormone metabolism in domestic animals is of
obvious importance in animal husbandry, and as in the case of man the
investigation of urinary metabolites can provide much valuable information. However, whereas urinary steroids have been thoroughly investigated in man and much emphasis has been placed on the development of reliable methods for the measurement of these steroids, comparatively little work has been done along the same lines with domestic
animals.
From a review of existing knowledge (162) it would appear that
different species show quite different excretory patterns (Table IV). The