30
of the acid-base equilibrium therein.
Among higher verte-
brates,
it has been shown to function in the acid secretions
of the
gastric mucosa and the renal cortex and in the basic
secretion of the
pancreas.
C02 gas may be considered, not
only as a residue of an organism, but as an intermediary metabolite in various syntheses.
The work of Maetz and of Skinazi
(1953) on the carbonic anhydrase activity of the gas gland of
the perch suggests that the COy secreted has its origin in the
tissue cells rather than the blood, since an inhibitor of the
enzyme was found in the plasma of the perch.
The fact that
inhibition of the secretion of CO2g gas in the swim bladder
(by injection of carbonic anhydrase inhibitors) is followed by
a reduction in the production of oxygen,
favors Haldane's
(1922)
theory that the oxygen secreted comes from the dissociation of
oxyhaemoglobin in the gas gland.
Maetzreview of the biological
role of carbonic anhydrase shows that, among the higher as well
as the lower vertebrates, CO> gas, the enzyme substrate,
is a
factor of numerous regulations which assure the stability of the
internal environment and which maintain the acid-base equilibrium
in tissues having intense metabolic activity.
In a comparison of blood carbonic anhydrase in 15 species
of mammals, ranging in size from 0.006 to 600 kg,
Schmidt-Nielsen
(1960)
found that,
Larimer and
in general, the red cells of