Dual effect of prostaglandins on isolated intraocular porcine ciliary arteries

Abstract

ABSTRACT.Purpose: Prostaglandin analogues are used to reduce the intraocular pressure (IOP) in glaucoma, but also affect the tone of the arteries supplying the ciliary body. Previously, the effect of prostaglandins has been studied on the extraocular ciliary arteries, whereas the effect on intraocular ciliary arteries has not been studied in detail. Methods: Intraocular long posterior porcine ciliary arteries were isolated and mounted in a myograph system for isometric tension recording, and the effects of PGF 2a , the prostaglandin analogue latanoprost, PGD 2 , PGE 2 , PGI 2 and the thromboxane analogue U46619 were studied in the presence and absence of selective receptor antagonists. Results: The prostaglandins PGD 2 and PGE 2 induced relaxation at low concentrations (10 )9 -3 · 10 )7 m), which could be inhibited by blocking either the DP or the EP 4 receptor, whereas PGD 2 , PGE 2 , PGF 2a , latanoprost and U46619 induced contraction at high concentrations (10 )6 -10 )5 m), which could be inhibited by blocking the TP receptor. Additionally, blocking of the FP receptor induced a right-shift of latanoprost-induced contraction. Conclusions: Prostaglandins with affinity to DP 1 and EP 4 receptors induce relaxation at low concentrations, and prostaglandins with affinity to TP and FP receptors induce contraction at high concentrations of intraocular porcine ciliary vessels in vitro. The findings may contribute to understanding the regulation of blood flow to the ciliary body.

Purinergic Mechanisms and Prostaglandin E Receptors Involved in ATP-Induced Relaxation of Porcine Retinal Arterioles in vitro

“…A similar reduction of relaxation was observed in the presence of the EP 1 receptor antagonist SC 19220 which suggests that the effect had been mediated by prostaglandin E or other prostaglandins acting on this receptor in the vascular wall. Although a study has shown that prostaglandin E may elicit constriction of retinal arterioles [27], the present findings are consistent with several previous studies using the same model on both retinal and ciliary porcine arterioles [5,28,29]. Since ATP-γS-induced relaxation was unaffected by ibuprofen and EP 1 receptor antagonism, it is likely that the effect had been mediated by a degradation product from ATP.…”

“…Additionally, the presence of dual effects of purines on vascular tone with opposite responses at different concentrations and after different time lags [13,24] is supported by a previous study where adenosine was found to contract retinal arterioles at intermediate concentrations mediated by the A 1 and A 3 receptors and relaxation at high concentrations mediated by the A 2A and A 2B receptors [33]. The findings supplement previous studies, which showed that hypoxia-induced relaxation of porcine retinal arterioles and ciliary arteries is mediated by the EP 4 receptor [28,29] and thus adds to our understanding of the complexity of prostaglandin-induced tone regulation in retinal arterioles.…”

Diameter Changes of Retinal Arterioles During Acute HypoxiaIn Vivoare Modified by the Inhibition of Nitric Oxide and Prostaglandin Synthesis

“…The observed effect could not be shown in a study based on a smaller number of observations, 22 but may be due to the fact that the unspecific COX-inhibitor diclofenac had antagonized the synthesis of several prostaglandin with opposite effects as shown in in vitro experiments. 23,24 This points to the need for studying the involvement of individual prostaglandins on pressure autoregulation of retinal arterioles.…”

Acide arachidonique et prostaglandines : impact sur la formation des adipocytes blancs, bruns et brites/beiges

“…Cette prostaglandine peut activer un ou plusieurs de ses propres récep-teurs (EP1, EP2, EP3 et EP4) de manière dose dépendante (Fig. 2) [39]. L'interaction avec ses différents récepteurs permet l'induction de signaux intracellulaires différents.…”