1 The receptors for glutamic acid (L-Glu) present in the guinea-pig myenteric plexus-ileal longitudinal muscle preparation have been studied by measuring the muscle contraction induced by numerous putative endogenous agonists acting at these receptors. Furthermore, the actions of different concentrations of antagonists, glycine, Mg2 + and Ca2+ on the ileal contractions induced by L-Glu have been evaluated. 2 The EC5o values of the most common putative endogenous agonists of these receptors were:
Several corneal pathologies are characterized by the presence of reactive oxygen species (ROS); therefore, we evaluated the protection afforded by pirenoxine and melatonin to corneal cell culture and whole rabbit cornea from ultraviolet exposure and other oxidant systems.Rabbit cornea cell (SIRC) plates and whole corneas were exposed to UV-B (80 or 800 mJ/cm 2 ) or incubated with fMLPstimulated autologous macrophages, in the presence or absence of pirenoxine or melatonin (10 À5 M). The protective activity of compounds was assessed by measuring superoxide anion formation, inhibition of oxidation and mitochondrial viability. Moreover the ex vivo protective effect of pirenoxine and melatonin was verified in the whole cornea submitted to UV-B exposure in vitro.Our experimental data demonstrate that pirenoxine and melatonin were able to inhibit the superoxide formation and oxidative effect in cell culture and whole rabbit corneas submitted to UV-B exposure or to incubation with fMLP-stimulated autologous macrophages.Mitochondrial viability was restored in epithelial cells of rabbit cornea but not in SIRCs. Moreover, both compounds are also able to increase ex vivo epithelial corneal cell defences against the in vitro UV-B induced lipid peroxidation.
1 Our previously published data indicate that an endogenously produced 5-lipoxygenase metabolite can strongly contract isolated endothelium-preserved rat aortic strips when cyclo-oxygenase isoenzymes are inhibited. Therefore, we decided to investigate if cysteinyl-containing leukotrienes (Cys Lts) are involved in this endothelium-dependent contraction. 2 The isometric contraction of endothelium-preserved rat aortic strips was recorded in preparations preincubated with 5 mM indomethacin and precontracted with phenylephrine, adjusting resting tension at 0.7 g. Acetylcholine (ACh) contracted control strips. Montelukast and MK-571, selective type 1 Cys Lts receptor (Cys Lt 1 ) antagonists and the Cys Lt 1 /Cys Lt 2 (type 2 Cys Lts receptor) antagonist BAYu9773 dose-dependently prevented ACh-induced contraction, their IC 50 s being 2.2, 3.1 and 7.9 nM respectively. The leukotriene B4 receptor antagonist U75302 was far less potent (IC 50 1.5 mM).
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