Involvement of Nitric Oxide in the Regulation of Regional
Hemodynamics in Streptozotocin-Diabetic Rats
E. GRANSTAM1, S.-O. GRANSTAM2
Departments of 1Neuroscience/Ophthalmology and 2Medical
Sciences, University Hospital, Uppsala, Sweden
Received February 8, 2002
Accepted June 24, 2002
Summary
In experimental and human diabetes mellitus, evidence for an
impaired function of the vascular endothelium has been found and
has been suggested to contribute to the development of vascular
complications in this disease. The aim of the study was to
evaluate possible regional hemodynamic in vivo differences
between healthy and diabetic rats which would involve nitric
oxide (NO). Central hemodynamics and regional blood flow (RBF)
were studied using radioactive microspheres in early
streptozotocin (STZ)-diabetic rats and compared to findings in
healthy control animals. This method provides a possibility to
study the total blood flow and vascular resistance (VR) in
several different organs simultaneously. L-NAME iv induced
widespread vasoconstriction to a similar extent in both groups.
In the masseter muscle of both groups, acetylcholine 2 g/kg per
min, induced a RBF increase, which was abolished by pretreatment
with L-NAME, suggesting NO as a mediator of vasodilation. In the
heart muscle of both groups, acetylcholine alone was without
effect while the combined infusion of acetylcholine and L-arginine
induced an L-NAME-sensitive increase in RBF. The vasodilation
induced by high-dose acetylcholine (10 g/kg per min) in the
kidney was more pronounced in the STZ-diabetic rats. The results
indicate no reduction in basal vasodilating NO-tone in the
circulation of early diabetic rats. The sensitivity to
vasodilating effects of acetylcholine at the level of small
resistance arterioles vary between tissues but was not impaired
in the diabetic rats. In the heart muscle the availability of L-arginine
was found to limit the vasodilatory effect of acetylcholine in
both healthy and diabetic rats. In conclusion, the results
indicate a normal action of NO in the investigated tissues of
the early STZ-diabetic rat.
Key
words
Blood flow • Diabetes mellitus • Hemodynamics • Nitric
oxide • Rat
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Elisabet
Granstam, MD, PhD, Department of Neuroscience and Ophthalmology,
University Hospital, S-751 85 Uppsala, Sweden. FAX +46-18-504
857 E-mail:
elisabet.granstam@nc.uas.lul.se
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