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Erectile dysfunction (ED) affected the lives of more than 300 million men worldwide. Erectile dysfunction drugs (EDD), known as phosphodiesterase inhibitors (PDEIs), have been used for treatment of ED. It has been shown that oxidative stress plays an important role in the progression of erectile dysfunction. Oxidative stress can be alleviated or decreased by antioxidant enzymes. Therefore, the present study aims at investigating the changes in the activity of antioxidant enzymes such as superoxide dismutase, catalase, and glutathione reductase as well as protein expression of glutathione peroxidase and glutathione S-transferase after treatment of male rats with a daily dose of sildenafil (1.48 mg/kg), tadalafil (0.285 mg/kg) and vardenafil (0.285 mg/kg) for three weeks. In addition, levels of reduced glutathione and malondialdyhyde (MDA) were assayed. The present study showed that sildenafil, vardenafil, and tadalafil treatments significantly decreased the levels of glutathione, MDA and the activity of glutathione reductase. In addition, vardenafil and sildenafil increased the activity of superoxide dismutase and catalase. Interestingly, western immunoblotting data showed that vardenafil induced the activity of glutathione peroxidase (GPX) and its protein expression, whereas tadalafil and sildenafil inhibited such enzyme activity and its protein expression. In addition, the protein expression of GST π isozyme was markedly reduced after treatment of rats with sildenafil. It is concluded that ED drugs induced the activities of both SOD and catalase which consequently decreased MDA level. Therefore, decrement in MDA levels could increase nitric oxide–cGMP level which in turn promotes the erection mechanism.

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One of the most important fields of research dealing with the use of carbon-, basalt-, and glass-fiber composites in the civil construction industry is their behavior under various chemical exposure conditions. Fiber-reinforced-polymer composites used as internal and external reinforcement in various structural applications can be subjected to widely differing pH situations. This study investigated the chemical durability of various carbon, basalt and glass fibers. The fibers were immersed in four types of solutions with acid, saline, alkaline, and deionized-water conditioning schemes. The fiber mass loss and surface damage along with changes due to chemical reactions were observed through weight-loss measurements and scanning electron microscopy. A criterion was developed to characterize the performance of fibers as very good, good, fair, and poor. This methodology can also be used by manufacturers as a quick quality-control tool for evaluating the chemical resistance of different fibers prior to large-volume production. The results reveal that the carbon fibers exhibited higher chemical resistance than the basalt and glass fibers based on weight loss and evidence of chemical reactions. Moreover, the determination of the fiber chemical composition before and after conditioning in acid and alkaline solutions clearly shows that the E-glass fibers, which are known to contain boron, were very sensitive to chemical corrosion. The ECR-glass fibers showed excellent chemical durability, even better than the basalt fibers.

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