Macro- and microvascular complications
are common in diabetes mellitus and
accumulating evidence has shown that
insulin has a relevant effect on
cardiovascular function. A vasorelaxing
effect, attenuation of vasopressor response
to angiotensin and epinephrine and
reduction of vascular resistance have been
demonstrated for insulin. In contrast,
insulin is also known to stimulate
sympathetic nerves, -enhance Na
reabsorption in the kidney, alter Ca and Mg
ion movement and increase norepinephrineinduced
vasoconstriction. Insulin resistance
has been linked to the development of
essential hypertension. The balance
between the pervioui effects markedly
contributes to either the normality of BP or
setting the hypertension conditions. The
present study is designed to compare the
regional blood flow in four different arterial
resistance beds (carotid, renal, mesenteric
and hindquarter vascular beds) in control
versus streptozotocin induced diabetic rats
(which represents a model of type I
diabetes) and to investigate any possible
change in the vascular reactivity of these
beds to different pressor and dilator
substances in the streptozotocin induced
abetic rats. Blood flow in carotid, renal,
mesenteric and hindquarter vascular beds
was determined in normal and in streptozotocin induced diabetic rats.
Vascular conductance was calculated as
Flow / Pressure and DRCs of vascular
conductance were constructed in the four
vascular beds after the administration of
the a l-drenoceptor agonist, phenypherine;
the a2-drenoceptor agonist, clonidine; the p
drenoceptor agonist, isoprenaline; ATII; the
nitric oxide synthetase inhbitor, L-NAME
and the cyclo-oxygenase inhbitor,
indomethacin. The results demonstrated
that in streptozotocin induced diabetic rats,
regional blood flow was markedly reduced
especially in the renal and hindquarters
vascular beds. No change observed in the
blood flow to the mesenteric bed. An
enhanced response to the VC effect of
clonidine, angiotensin and L-NAME was
observed. No change was observed in a Idrenoceptor-
mediated responses. An
attenuated response to the VD effect of the
isoprenaline and indomethacin was
determined. Theses results suggest an
impaired vascular responses in diabetes
that possiblely involve endothelium,
prostglandins, a2 and p adrenoreceptors. |
