Vasoactive properties of bimatoprost in isolated porcine ciliary arteries

Background: To investigate the vasoactive effect of bimatoprost (Lumigan(R)), a new topical ocular hypotensive agent, in isolated porcine ciliary arteries. Material and methods: Arteries were placed in a myograph system to measure isometric forces. Quiescent vessels as well as vessels pre-contracted with either 10 nM endothelin-1 or 100 mM potassium chloride (KCl) were exposed, in a cumulative manner, to increasing concentrations (0.1 nM-0.1 mM) of bimatoprost (dissolved in ethanol). in quiescent vessels, results were expressed in percent of 100 mM KCl-induced contraction. In endothelin-1-pre-contracted vessels, results were expressed in percent of the maximal contraction induced by endothelin-1. In KCl-pre-contracted vessels, results were expressed in percent of the plateau contraction reached 30 minutes after 100 mM KCl application. Results: Bimatoprost induced a significant (p < 0.05 - 0.001) vasoconstriction at concentrations equal to or higher than 0.1 mu M in quiescent vessels (0.1 mM: 73 +/- 12%). In KCl-pre-contracted vessels, at concentrations higher than 1 mu M bimatoprost induced significant (p < 0.05 - 0.01) contractions (0.1 mM: 67 +/- 17%). In endothelin-1-pre-contracted vessels, bimatoprost also induced significant (p<0.05-0.001) contractions at concentrations above 10 mu M (0.1 mM: 17 +/- 8%). Conclusions: The present study indicates that bimatoprost appears to have, in vitro, some vasoactive properties in porcine ciliary arteries. The question whether Lumigan(R) has an influence on ocular blood flow needs to be further investigated.