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  • Title: L-NAME- and U 46619-induced contractions in isolated porcine ciliary arteries versus vortex veins.
    Author: Pellanda N, Flammer J, Haefliger IO.
    Journal: Klin Monbl Augenheilkd; 2001 May; 218(5):366-9. PubMed ID: 11417338.
    Abstract:
    PURPOSE: To investigate contractions evoked by the thromboxane A2 analog U 46619 and by the inhibitor of nitric oxide formation NG-nitro-L-arginine methyl ester (L-NAME) in isolated porcine ciliary arteries and vortex veins. MATERIAL AND METHODS: In a myograph system (for isometric forces measurement), vessels were exposed (at different levels of wall tension) to 100 mM potassium chloride (KCl). At their optimal tension, vessels were exposed (in a cumulative manner) to increasing concentrations of U 46619 (0.1 nM-1 microM) in the absence or in the presence of L-NAME (0.1 mM). Contractions were expressed in mN or in percent of a 100 mM KCl-induced contraction. RESULTS: Optimal tension was higher in arteries (7 mN) than in veins (3 mN). Maximal contractions induced by KCl were stronger in arteries (24.4 +/- 3.6 mN; n = 8) than in veins (1.8 +/- 0.2 mN; n = 8). In contrast, maximal contractions evoked by U 46619 were proportionally higher (p < 0.001) in veins (178.3 +/- 8.9%; n = 8) than in arteries (108.4 +/- 2.6%; n = 5) and were not significantly affected by L-NAME. Sensitivity to U 46619 was not significantly different between arteries (pD50 = 7.7 +/- 0.1) and veins (pD50 = 7.9 +/- 0.1). In quiescent vessels, L-NAME evoked contractions that were higher (p < 0.001) in veins (43 +/- 7.9%; n = 13) than in arteries (7.5 +/- 1.7%; n = 10). CONCLUSIONS: When compared with KCl-induced contractions, contractions evoked by U 46619 or L-NAME are proportionally higher in porcine vortex veins than in ciliary arteries.
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