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T. Goseki, K. Shimizu, H. Ishikawa, H. Nishimoto, K. Mashimo, S. Uga, T. Yoshitomi; Vascular Reactivity in Isolated Hyperglycemic Rabbit Ciliary Artery. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2282.
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© ARVO (1962-2015); The Authors (2016-present)
The purpose of the present study is to investigate the functional and morphological changes occurring in the ciliary artery wall of rabbits with alloxan-induced diabetes mellitus.
A single intravenous bolus injection of alloxan (100 mg/kg) was given to each of 26 10-week-old rabbits and 16 sham-injected control rabbits. Twenty weeks later, control rabbits and diabetic rabbits were sacrificed, and their ciliary arteries were mounted in a myograph system. The responses of these arteries to high K+ solution (K-Krebs solution), phenylephrine and carbachol were investigated using isometric tension recording. L-NAME (NG-nitro-L-arginine methyl ester; 100 mM) was also used to test the mechanism causing the carbachol induced relaxation. The arteries were also examined morphologically.
The maximum tensions induced by K-Krebs solution and phenylephrine caused dose-dependent contraction with EC50 values were not significantly different between the two. Carbachol induced dose-dependent relaxations in segments precontracted with K-Krebs solution. These relaxations were significantly reduced in the diabetic rabbits. The maximum relaxation induced by carbachol was 77.0±2.4% (10 mM) and 66.4±2.5% (100 mM) in the control and diabetic rabbits, respectively. These values were significantly different (P=0.0076). Application of a 100 mM nitric oxide synthase inhibitor, L-NAME, significantly inhibited the amplitude of relaxations evoked by carbachol. Histologically, the frequency of invaginations was less in the diabetic arterioles with a flattening of the lamina in the diabetic rabbits than in the controls. The cytoplasm of endothelial cells contained large vacuoles, indicating weak adhesion to the lamina. Some endothelial cells even showed vacuolar degeneration due to breakdown of the cell membranes. However, the smooth muscle cells were well preserved in the diabetic rabbit.
These results suggest that the mechanism of impairment of ocular circulation induced by diabetes mellitus is mainly the reduction of NO synthase due to endothelial cell dysfunction. Furthermore, the characteristics of rabbits with alloxan-induced diabetes mellitus probably make them a useful model for investigating ocular complications induced by diabetic mellitus.
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