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Reduction of diabetes-induced oxidative stress by phosphodiesterase inhibitors in rats.

Milani E, Nikfar S, Khorasani R, Zamani MJ, Abdollahi M.

Laboratory of Toxicology, Department of Pharmacology and Toxicology, Faculty of Pharmacy, and Pharmaceutical Sciences Research Center, Tehran University of Medical Sciences, Tehran, Iran.

Increased oxidative stress has been suggested to be involved in the pathogenesis and progression of diabetic tissue damage. The aim of this study was to investigate the effect of different phosphodiesterase inhibitors on lipid peroxidation and total antioxidant capacity (TAC) of plasma in streptozotocin-induced diabetic rats (Rattus norvegicus). Rats became diabetic by a single administration of streptozotocin (STZ, 45 mg/kg). The effects of 15-days treatment by milrinone, sildenafil, and theophylline as cyclic-AMP and -GMP phosphodiesterase inhibitors (PDEIs) on diabetes-induced oxidative stress were studied. The levels of glucose, malonedialdehyde (MDA) the by product of lipid peroxides, and TAC (FRAP test) were estimated in plasma of control and experimental groups of rats. A significant increase in the levels of plasma glucose, and MDA and a concomitant decrease in the levels of TAC were observed in diabetic rats. These alterations were reverted back to near normal level after the treatment with PDEIs. Treatment of diabetic rats by PDEIs reduced MDA levels and increased TAC in the order of milrinone>sildenafil>theophylline. In conclusion, the present investigation show that PDIS possesses antioxidant activities, which may be attributed to their enhancing effect on cellular cyclic nucleotides contributing to the protection against oxidative stress in streptozotocin-induced diabetes. Exact mechanism of protective actions of cAMP- and cGMP-phosphodiesterase remains to be elucidated by further studies. This finding may suggest a place for PDEIs in maintaining health in diabetes.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15907769&query_hl=1

[Quality control in the urologist's practice Erectile dysfunction as an example of a multi-centered approach to documenting treatment results in urologist practices.]

[Article in German]

Junemann KP, Cassens S, Lippert H, Burkart M.

Klinik fur Urologie und Kinderurologie, Universitatsklinikum Schleswig-Holstein, Campus Kiel, Kiel.

Of 517 urologist practices approached, 93% participated in a pilot study on the quality of care in the treatment of erectile dysfunction (ED). Treatment modalities and satisfaction were documented for 10,750 ED patients in 2002-at a time when vardenafil and tadalafil had not yet been officially approved. Psychological factors (55%), BPH (42%), and hypertension (33%) were given as the most prevalent ED risk factors; 82% of the patients received sildenafil, 20% apomorphine, 12% yohimbine, and 10% intracavernous alprostadil. Of the patients, 81% were satisfied or very satisfied with one of the treatment options offered and 85% and more were satisfied or very satisfied with sildenafil's onset of action, duration of action, efficacy, and tolerability. Of the physicians, 97% rated the opportunity to compare their own treatment results with other urologists' results as important or very important.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15905987&query_hl=1

The multidrug resistance protein 5 (ABCC5) confers resistance to 5-fluorouracil and transports its monophosphorylated metabolites.

Pratt S, Shepard RL, Kandasamy RA, Johnston PA, Perry W 3rd, Dantzig AH.

Cancer Research, Lilly Research Laboratories, Lilly Corporate Center, Indianapolis, IN 46285, USA.

5'-Fluorouracil (5-FU), used in the treatment of colon and breast cancers, is converted intracellularly to 5'-fluoro-2'-deoxyuridine (5-FUdR) by thymidine phosphorylase and is subsequently phosphorylated by thymidine kinase to 5'-fluoro-2'-dUMP (5-FdUMP). This active metabolite, along with the reduced folate cofactor, 5,10-methylenetetrahydrofolate, forms a stable inhibitory complex with thymidylate synthase that blocks cellular growth. The present study shows that the ATP-dependent multidrug resistance protein-5 (MRP5, ABCC5) confers resistance to 5-FU by transporting the monophosphate metabolites. MRP5- and vector-transfected human embryonic kidney (HEK) cells were employed in these studies. In 3-day cytotoxicity assays, MRP5-transfected cells were approximately 9-fold resistant to 5-FU and 6-thioguanine. Studies with inside-out membrane vesicles prepared from transfected cells showed that MRP5 mediates ATP-dependent transport of 5 micromol/L [(3)H]5-FdUMP, [(3)H]5-FUMP, [(3)H]dUMP, and not [(3)H]5-FUdR, or [(3)H]5-FU. The ATP-dependent transport of 5-FdUMP showed saturation with increasing concentrations and had a K(m) of 1.1 mmol/L and V(max) of 439 pmol/min/mg protein. Uptake of 250 micromol/L 5-FdUMP was inhibited by dUMP, cyclic nucleotide, cyclic guanosine 3',5'-monophosphate, amphiphilic anions such as probenecid, MK571, the phosphodiesterase inhibitors, trequinsin, zaprinast, and sildenafil, and by the chloride channel blockers, 5-nitro-2-(3-phenylpropylamino)-benzoic acid and glybenclamide. Furthermore, the 5-FU drug sensitivity of HEK-MRP5 cells was partially modulated to that of the HEK-vector by the presence of 40 micromol/L 5-nitro-2-(3-phenylpropylamino)-benzoic acid but not by 2 mmol/L probenecid. Thus, MRP5 transports the monophosphorylated metabolite of this nucleoside and when MRP5 is overexpressed in colorectal and breast tumors, it may contribute to 5-FU drug resistance.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15897250&query_hl=1

Use of tadalafil in a patient with a secondary Raynaud's phenomenon not responding to sildenafil.

Baumhaekel M, Scheffler P, Boehm M.

Department of Cardiology and Angiology, University Hospital of the Saarland, Kirrbergerstr., 66421 Homburg/Saar, Germany.

The Raynaud's phenomenon often accompanies systemic rheumatic diseases and is also known as a vascular side effect of chemotherapy. Therapy of the Raynaud's phenomenon with nitrates or calcium-channel-blockers is rarely beneficial. In contrast, the PDE-V-inhibitor sildenafil seems to be effective in these patients. For the first time we report on a patient with Raynaud's phenomenon due to chemotherapy not responding to sildenafil but to the new PDE-V-inhibitor tadalafil in an equivalent dosage. Measurement with a laser Doppler revealed an increased blood flow and a reduction of symptoms. Therefore, therapy of Raynaud's phenomenon with the new PDE-V-inhibitor tadalafil seems to be an effective treatment option in patients not responding to sildenafil.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15896360&query_hl=1