4. SPECIES DIFFERENCES IN BILE SALTS
211
The resulting bile salt is similar to the taurine (NH 2
# CH 2
# CH 2 *S0 3 H)
conjugates which occur with all bile acids (R'COOH) and have the
general formula R'CO
# NH
# CH 2
# CH 2
# S0 3 ~. In some mammals there are
also glycine (NH 2 -CH 2 -COOH) conjugates of bile acids (R-COOH),
and these must exist partly as R*CO
# NH-CH 2 *COOH molecules and
partly as the ions R*CO*NH*CH 2 *COO-. The precise distribution of
glycine conjugation is not known; it may possibly be confined to the
Eutheria. A few vegetarian species (e.g., rabbit, pig, coypu) have a
very high proportion of their bile acids in glycine conjugation, although
taurine conjugates do occur in these animals (see, e.g., reference 54).
In the human infant, glycine conjugation is only gradually established
(48).
II. Distribution
The distribution of the different types of bile salts referred to above
is shown in Table I. In this table, findings are given as stated in the
original literature. Where the present writer or the author of the work
regards the findings as doubtful, this is indicated by a query (?).
Nomenclature of species is shown, in general, as it appears in the original
publications.
III. Bile Salts as a Species Character
A. GENERAL
The information in Table I may be taken as substantially correct,
and it shows that there are definite species variations in the chemical
nature of bile salts. Apart from the evolutionary aspect, discussed below,
one may notice that closely related species have similar bile salts and
that these are sometimes confined to a single group. For example, all the
Cyprinidae examined have cyprinol, two of the three investigated species
of Ranidae have ranol, all the Boidae have pythocholic acid, the only
two snakes examined of the genus Bitis have bitocholic acid, and only
Suidae have hyocholic acid and its relatives. In larger groups, the
Selachii have scymnol, Chelonia have tetrahydroxysterocholanic acid,
and all the Pinnipedia, phocaecholic acid. On the other hand, distribution of some substances (for example, the trihydroxycoprostanic acids,
Ohta's acid, deoxycholic acid, ursodeoxycholic acid and the keto acids)
is "patchy" and apparently not governed by evolutionary relationships;
perhaps the same remarks should apply to glycine conjugation. Thus, it
is clear that if bile salts are to be used as a species character, care will
have to be taken in selecting substances for this purpose. Valuable
211
The resulting bile salt is similar to the taurine (NH 2
# CH 2
# CH 2 *S0 3 H)
conjugates which occur with all bile acids (R'COOH) and have the
general formula R'CO
# NH
# CH 2
# CH 2
# S0 3 ~. In some mammals there are
also glycine (NH 2 -CH 2 -COOH) conjugates of bile acids (R-COOH),
and these must exist partly as R*CO
# NH-CH 2 *COOH molecules and
partly as the ions R*CO*NH*CH 2 *COO-. The precise distribution of
glycine conjugation is not known; it may possibly be confined to the
Eutheria. A few vegetarian species (e.g., rabbit, pig, coypu) have a
very high proportion of their bile acids in glycine conjugation, although
taurine conjugates do occur in these animals (see, e.g., reference 54).
In the human infant, glycine conjugation is only gradually established
(48).
II. Distribution
The distribution of the different types of bile salts referred to above
is shown in Table I. In this table, findings are given as stated in the
original literature. Where the present writer or the author of the work
regards the findings as doubtful, this is indicated by a query (?).
Nomenclature of species is shown, in general, as it appears in the original
publications.
III. Bile Salts as a Species Character
A. GENERAL
The information in Table I may be taken as substantially correct,
and it shows that there are definite species variations in the chemical
nature of bile salts. Apart from the evolutionary aspect, discussed below,
one may notice that closely related species have similar bile salts and
that these are sometimes confined to a single group. For example, all the
Cyprinidae examined have cyprinol, two of the three investigated species
of Ranidae have ranol, all the Boidae have pythocholic acid, the only
two snakes examined of the genus Bitis have bitocholic acid, and only
Suidae have hyocholic acid and its relatives. In larger groups, the
Selachii have scymnol, Chelonia have tetrahydroxysterocholanic acid,
and all the Pinnipedia, phocaecholic acid. On the other hand, distribution of some substances (for example, the trihydroxycoprostanic acids,
Ohta's acid, deoxycholic acid, ursodeoxycholic acid and the keto acids)
is "patchy" and apparently not governed by evolutionary relationships;
perhaps the same remarks should apply to glycine conjugation. Thus, it
is clear that if bile salts are to be used as a species character, care will
have to be taken in selecting substances for this purpose. Valuable