The little studied plasma kallikrein-kinin system of
poikilotherm vertebrates was investigated in several species
offish, amphibians, and reptiles, and compared to the well-known mammalian enzyme system. It was found that the plasmas
of all fish and amphibians tested differed from reptilian and
mammalian plasma in their inability to release a kinin-like
factor when reacted with trypsin or glass, and no evidence
was obtained to suggest that these plasmas contain enzymic
machinery which can produce a kinin. However, it was shown
that heat-denatured plasma from these animals did develop
biological activity when treated with hog pancreas kallikrein,
an enzyme specific for releasing kinins. Thus, the equivalent of a kininogen might exist in these plasmas.
Since turtle plasma produced a kinin by endogenous enzymes,
detailed studies of this system were conducted. By
a variety of criteria, enzymic mechanisms for kinin production
in this plasma were closely similar to those of mammalian
plasma. However, purification of the turtle kinin released
by endogenous enzymes, followed by pharmacological and chemical tests showed that this kinin was chemically different
from bradykinin, its mammalian counterpart. Data obtained from amino acid analysis of the peptide, and from certain pharmacological tests, strongly suggested that the structure
of turtle kininis 6-thr-bradykinin; i.e., that a threonine
residue has been substituted for a serine . The possible significance of this finding is discussed.
Preliminary studies of the pharmacological effects of
bradykinin on aspects of blood pressure and flow in the turtle
itself are described. Intra-arterial injections of bradykinin
over a wide range of doses always produced a press or response
which could be greatly reduced by adrenergic blockade. This
is in contrast with the effect of, the peptide in mammals,
where there is typically a hypotensive response which cannot be
reduced by adrenergic blockade. The significance of this difference
is discussed, and approaches to future investigations
are suggested. / Science, Faculty of / Zoology, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/41219 |
| Date | January 1971 |
| Creators | Dunn, Rex Stewart |
| Publisher | University of British Columbia |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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