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K. Holmgaard, T. Bek; Prostaglandin E Induces Retina Dependent Relaxation of Porcine Retinal Arterioles in vitro. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3445.
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Previous studies have shown that inhibition of prostaglandin synthesis can prevent relaxation of retinal arterioles induced by N-methyl-D-aspartic acid (NMDA) and adenosine tri-phosphate (ATP) from the perivascular retinal tissue. The purpose of the present study was to identify prostaglandins involved in this retina dependent relaxation.
Porcine retinal arterioles were mounted in a wire-myograph for isometric tone measurements. The effect of PGE2, PGF2α, PGD2, PGI2 and TXA2 on vascular tone was recorded with and without pre-contraction with the prostaglandin analogue U46619, and before and after removal of the perivascular retina. The specificity of the prostaglandin induced effects was confirmed by blocking with specific antagonists.
All the tested prostaglandins showed a signficant relaxation of pre-contracted arterioles (p<0.01, repeated measurements ANOVA). PGF2α showed a significant constriction on isolated non-contracted arterioles (p<0.01, repeated measurements ANOVA), whereas PGD2 induced a dual response with a significant constriction at low concentrations and a signficant dilatation at high concentrations (p<0.01, repeated measurements ANOVA). In arterioles with surrounding perivascular tissue, the vasorelaxing effect of PGE2 was significantly increased (p<0.01, repeated measurements ANOVA), and this effect could be antagonized by an EP1 receptor blocker.
PGE2 induces a receptor specific retina dependent relaxation of pre-constricted porcine retinal arterioles. This suggests an involvement of PGE2 in retina dependent relaxation of retinal arterioles. Further investigations are needed to elucidate the exact role of PGE2 in the sequence of events leading to relaxation of retinal arterioles.
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