L-NAME- and U 46619-induced contractions in isolated porcine ciliary arteries versus vortex veins.
OBJECTIVE
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.


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.
Pellanda
N
N
Laboratory of Ocular Pharmacology and Physiology, University Eye Clinic Basel, Mittlere Strasse 91, PO Box, CH-4012 Basel.
Flammer
J
J
Haefliger
I O
IO
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology*; D000818:Animals; D019842:Ciliary Arteries / Q000187:drug effects*; D002924:Ciliary Body / Q000098:blood supply*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D013552:Swine; D013928:Thromboxane A2 / Q000031:analogs & derivatives*; D014661:Vasoconstriction / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D014680:Veins / Q000187:drug effects
D004791:Enzyme Inhibitors; D014662:Vasoconstrictor Agents; D013928:Thromboxane A2; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester