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Original Article

Effect of dipyridamole on vascular responses of porcine ciliary arteries

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Pages 387-393 | Received 08 Aug 1995, Accepted 05 Dec 1995, Published online: 02 Jul 2009
 

Abstract

This study investigated the effects of dipyridamole in isolated porcine ciliary arteries (diameter 200–250 μm).

Isolated porcine ciliary arteries were suspended in myograph chambers filled with modified Krebs-Ringer solution (37°C; 95% O2/5% CO2) for isometric tension recording.

Dipyridamole induced concentration-dependent relaxations of porcine ciliary arteries with endothelium precontracted with thromboxane analogue U-46619 (10-6M), KC1 (50 mM), or endothelin-1 (10-8M). Removal of the endothelium of the ciliary vessels and preincubation of the arteries with L-NAME (10-SM), or indomethacin (10-5M), or the combination of the two drugs significantly reduced the relaxation to dipyridamole (p = 0.002–0.03). Similar vascular responses could be observed in a time-dependant analysis of the effect of a single concentration dipyridamole (10-4M). The stimulator of CAMP forskolin also caused relaxations. Endothelin-1 (10-12-10-7M) and U-46619 (10 10-10−6M) induced potent contractions of porcine ciliary arteries. Preincubation with dipyridamole (10−5M) reduced contractions to endothelin-1 as compared to control (p < 0.004), while contractions to U-46619 were only slightly affected under these conditions (n.s.).

These findings demonstrate that dipyridamole is a vasodilator in porcine ciliary arteries. Endothelial nitric oxide and prosta-cyclin contribute importantly to the effects of dipyridamole. Further studies are required to show whether these properties of dipyridamole may also occur in vivo and offer clinical use in patients with ocular vasospasms and other ophthalmic vascular dysfunctions.

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