Ergin Singirik

Effect of tempol (4‐hydroxy tempo) on gentamicin‐induced nephrotoxicity in rats

We investigated the effects of tempol (4‐hydroxy tempo), a membrane‐permeable radical scavenger, on gentamicin‐induced renal failure in rats. The rats were given gentamicin (100 mg/kg/day, i.p., once a day); and gentamicin (100 mg/kg/day, i.p.) and tempol (3.5, 7 or 14 mg/kg/day, i.p., once a day). At the end of 7 days, the gentamicin group produced the remarkable nephrotoxicity, characterized by a significantly decreased creatinine clearance and increased serum creatinine, blood urea nitrogen (BUN) and daily urine volume when compared with controls. In control the BUN value was 21.2 ± 0.07 (mg/100 mL); in comparison, it was 96.9 ± 6.03 in gentamicin group (P < 0.05). Renal histopathologic examination confirmed acute tubular necrosis in this group. In rats treated with gentamicin and tempol a partial improvement in biochemical and histologic parameters was observed. BUN values were 96.9 ± 6.03 and 36.3 ± 2.39 in gentamicin, and gentamicin plus tempol (14 mg/kg) treated groups, respectively (P < 0.05). These results suggest that the administration of tempol may have a protective effect on gentamicin‐induced nephrotoxicity in rats.

Comparative study of the quercetin, ascorbic acid, glutathione and superoxide dismutase for nitric oxide protecting effects in mouse gastric fundus

The aim of this work was to compare the preventing capacity of quercetin with Cu/Zn superoxide dismutase (Cu/Zn SOD), ascorbic acid and glutathione on nitric oxide (NO)-induced relaxation in mouse gastric fundus. Furthermore, the effects of the quercetin on the tissue level of total oxidant and antioxidant was investigated. Nitrergic stimulation (4Hz, 25V, 0.1 ms, 10s-train) and exogenous NO (10 μM) induced relaxation. Pyrogallol (10 μM), hydroquinone (100 μM) and LY83583 (6-Anilino-quinolin-5,8-quinone, 5 μM) inhibited nitrergic relaxations. The inhibition observed with pyrogallol, hydroquinone and LY83583 was prevented by quercetin (0.1 μM). Also, ascorbic acid (500 μM), glutathione (100 μM) and Cu/Zn SOD (100 U/ml) prevented the inhibitory effect of superoxide anion generators on the relaxation to nitrergic stimulation and NO. Diethyldithiocarbamic acid (DETCA; 8mM) inhibited nitrergic relaxations. DETCA-induced inhibition on nitrergic stimulation and NO-induced relaxation was prevented by quercetin, ascorbic acid, glutathione or Cu/Zn SOD. DETCA plus pyrogallol, hydroquinone or LY83583 strengthened the inhibition on the relaxations. Also, pre-treatment with quercetin, ascorbic acid and glutathione prevented the inhibitory effect of DETCA plus LY-83583 on the relaxation to nitrergic stimulation and NO but Cu/Zn SOD did not prevent this inhibition. Also, quercetin increased tissue total antioxidant capacity and decreased tissue oxidant level and oxidative stress index in DETCA-treatment group. These results indicate that quercetin has antioxidant effect and protects NO from endogenous superoxide anion-driven inactivation and enhances its biological activity, suggesting that quercetin may scavenge superoxide anion in a Cu/Zn SOD, glutathione or ascorbic acid-inhibitable manner.

Neocuproine, a Copper (I) Chelator, Potentiates Purinergic Component of Vas Deferens Contractions Elicited by Electrical Field Stimulation

Effects of the specific copper (I) chelator, neocuproine, on the purinergic and adrenergic components of nerve-evoked contractions were investigated in the prostatic rat vas deferens. Electrical field stimulation (EFS; 4 Hz) induced bimodal contractions of vas deferens tissue in the presence of α1-adrenoceptor antagonist prazosin (to isolate the purinergic component) or purinoceptor antagonist suramin (to isolate the adrenergic component). Neocuproine significantly potentiated the purinergic component of the contractile responses to EFS. However, the same agent failed to elicit any significant effect on the adrenergic component of nerve-evoked contractions. The copper (II) chelator cuprizone could not affect the purinergic component of contractions. The potentiating effect of neocuproine which was reversible after washout of the drug, did not occur following the application of the pre-prepared neocuproine-copper (I) complex. A nitric oxide synthase inhibitor, L-nitroarginine; a cyclooxygenase inhibitor, indomethacin or an α2-adrenoceptor antagonist, yohimbine, failed to alter the responses to neocuproine on the purinergic component of the contraction to EFS. Neocuproine did not elicit any significant effect on preparations in which the purinergic receptors were desensitized with α,β-methylene ATP. In conclusion, our results suggest that neocuproine potentiates the purinergic component of rat vas deferens contractions elicited by EFS, presumably by facilitating purinergic neurotransmission and that copper (I)-sensitive mechanisms can modulate purinergic transmission in this tissue.

Protective effect of L-arginine on gentamicin-induced nephrotoxicity in rats.

Introduction: L-arginine has a protective effect on gentamicin-induced renal failure and it may decrease the tubular reabsorption of another cationic substance, gentamicin due to its cationic structure. The aim of this study is to compare the possible protective effects of L-arginine and its inactive isomer D-arginine on gentamicin-induced nephrotoxicity in rats. Materials and Methods: Wistar albino rats were housed in metabolic cages and assigned to six groups as: control group, gentamicin (100 mg/kg), gentamicin + L-arginine (2 g/l), gentamicin + D-arginine (2 g/l), gentamicin + L-arginine + Nv-nitro-L-arginine methyl ester (L-NAME) (100 mg/l) and gentamicin + D-arginine + L-NAME. Gentamicin was administered by subcutaneous injections and the other drugs were added in drinking water for seven consecutive days. The animals were killed by decapitation and intracardiac blood and urine samples were obtained on the seventh day. Blood urea nitrogen, serum creatinine, sodium, potassium, urine gamma glutamyl transferase, creatinine, sodium, potassium and gentamicin levels were measured using High Performance Liquid Chromatography (HPLC) technique. Results: Gentamicin treated group had significant increase in blood urea nitrogen, serum creatinine, fractional Na excretion and urine gamma glutamyl transferase levels, and significant decrease in creatinine clearance compared to the control group. L-arginine and D-arginine reversed these findings. L-NAME abolished the nephroprotective effect of L-arginine. The urinary levels of gentamicin were significantly increased in rats treated with L-arginine or D-arginine compared to those treated with gentamicin. L-arginine and D-arginine reversed the advanced degenerative changes due to gentamicin administration in histopathological examination. Conclusion: Our study revealed the protective effect of L-arginine on gentamicin-induced nephrotoxicity, the contribution of the cationic feature of L-arginine, and the major role of NO in this protective effect.

Effects of some divalent cations on nitrergic relaxations in the mouse corpus cavernosum.

Acute effects of some divalent cations (Cd2+, Ni2+, Co2+, Zn2+, Mn2+ and Sn2+) were investigated on neurogenic and endothelium‐dependent relaxations in the isolated mouse corpus cavernosum. Neither neurogenic nor endothelium‐dependent relaxation was affected by cations at the concentrations used (up to 100 μM), except Cd2+. Although Cd2+ (20 and 40 μM) did not cause any significant alteration in the acetylcholine‐ (ACh) or sodium nitroprusside‐ (SNP) induced relaxation, it inhibited electrical field stimulation‐ (EFS) produced relaxation significantly. Zn2+ and selenium could not reverse this inhibitory action. Cd2+ did block the EFS‐evoked guanethidine‐sensitive contraction in the presence of NG‐nitro‐L‐arginine. Elevation of external Ca2+ content significantly reduced the inhibitions due to Cd2+ on the EFS‐induced relaxation and on the EFS‐evoked guanethidine‐sensitive contraction. In the Ca2+‐omitted medium, EFS‐induced relaxation disappeared, while acetylcholine‐elicited relaxation resisted. Verapamil was ineffective on the relaxation produced by EFS or acetylcholine. However, it significantly diminished phenylephrine‐induced contractions. These findings suggest that unlike other cations at the concentrations used in the present study, Cd2+ may have an effect on an external Ca2+‐dependent mechanism at the neuronal level, and this effect may be responsible for its acute inhibitory action on the neurogenic relaxation in the mouse corpus cavernosum.