Antithrombotic Effects of Odorless Garlic Powder
89
thrombus formation by fibrin generation followed by
platelet aggregation, and thus it might be suitable for
observing the ordinary process of blood clot formation
by platelet and coagulation systems, which is frequently
caused by endothelial injury22) and blood flow disturb-
ance. Though the platelet system was not analyzed, the
coagulation factors were consumed in the control group,
indicating that both extrinsic and intrinsic pathways
were induced, as shown in the prolongation of PT and
APTT (Fig. 5A, B). This activation of the coagulation
system was confirmed by elevated thrombin activity (as
TAT) and FDP (Fig. 5C, D). Since FDP reflects the
degradation of fibrin, a significant amount of fibrin clot,
though not observed directly in the loop, was presum-
ably formed and subsequently degraded by the fibrino-
lytic system in the control rats. Under such conditions,
the rats administrated garlic exhibited significantly
reduced TAT and a tendency to decrease FDP, suggest-
ing that garlic considerably attenuated the formation of
thrombus in the model. This might essentially explain
how odorless garlic prevents pathological fibrin-throm-
bus formation in addition to platelet aggregation in
humans.
antithrombotic activity is specific to our garlic prepara-
tion. Since garlic possesses a lot of physiological
functions, the composition and the amounts of each
responsible element in the various functions may differ
among species and methods of manufacture. Thus it is
natural that the physiological functions of garlic are not
homogenous and depend on the amount of active
components as well as their combination in a garlic
preparation.
Therefore it has not yet been confirmed which
component contributes to the antithrombotic activity in
the rat model.
In summary, this odorless garlic powder did not
stimulate t-PA or PAI-1 in HUVECs, but it promoted
plasminogen activation by t-PA in vitro. In addition, the
garlic strongly reduced coagulation activity, which
would prevent blood-clot formation in the rat patholog-
ical thrombus model. These results may explain much
evidence that garlic and its preparations are beneficial
substances for blood and vasculature. Thus, our prepa-
ration of odorless garlic was found to be useful as a
supplement the mechanism of which is basically
characterized as antithrombotic function.
The antithrombotic property also refers to relaxing of
blood vessels (i.e. anti-hypertension), because enlarge-
ment of vessel interspace can help blood circulation in
occlusion by blood clot. We also measured two vaso-
motor factors from HUVECs stimulated by garlic. One
is the vasoconstriction protein endothelin-1 (ET-1) and
the other vasorelaxing substance nitric oxide (NO)
which can be measured as endothelial nitric oxide
synthase (eNOS). In contrast to the results that garlic
caused NO-dependent relaxation and inhibited ET-1-
induced constriction in rats,23) no significant changes in
ET-1 or eNOS expression were found in the presence
of garlic (data not shown). However, S-allyl cysteine
inhibited NO without changes in eNOS in HUVECs.24)
Thus the effects seemed to be different in humans and
rats, or else they depend on the component of garlic. Our
preparation of odorless garlic did not directly regulate
these factors in HUVECs. It remains to be analyzed
whether garlic can reduce hypertension in animals such
as the spontaneously hypertensive rat.
It has not yet been investigated which substances in
the garlic preparation were essentially involved in
antithrombotic function (such as the anticoagulation
effect by decreasing thrombin in the rat and such as the
hyperfibrinolytic effect by increasing t-PA activity on
fibrin film) evidenced in this study. Though allicin, one
of the major components in garlic, possesses several
biological activities,25) it seems that allicin does not
function in promoting t-PA activity, since the garlic
preparation contains less allicin in the process of
production due to inactivation of alliinase, thus being
odorless. However, it was uncertain whether alliin in the
diet was converted to allicin after it was taken into the
rats. We did not examine other garlic products with and
without odor. Thus, it is also uncertain whether the
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