The effects of daylight exposure on melatonin levels, Kiss1 expression, and melanoma formation in mice.

AIM: To determine how daylight exposure in mice affects melatonin protein expression in blood and Kiss1 gene expression in the hypothalamus. The second aim was to assess the relationship between skin cancer formation, daylight exposure, melatonin blood level, and kisspeptin gene expression level. METHODS: New-born mice (n=96) were assigned into the blind group or daylight group. The blind group was raised in the dark and the daylight group was raised under 12 hours light/12 hours dark cycle for 17 weeks. At the end of the 11th week, melanoma cell line was inoculated to mice, and tumor growth was observed for 6 weeks. At the end of the experiment, melatonin level was measured from blood serum and Kiss1 expression from the hypothalamus. RESULTS: The blind group had significantly higher melatonin and lower Kiss1 expression levels than the daylight group. Tumor volume was inversely proportional to melatonin levels and directly proportional to Kiss1 expression levels. Tumor growth speed was lower in the blind than in the daylight group. CONCLUSION: Melatonin and Kiss1 were shown to be nvolved in tumor suppression. They were affected by daylight and were mutually affected by each other.

Molecular basis of vascular damage caused by cigarette smoke exposure and a new approach to the treatment: Alpha-linolenic acid.

Exposure to cigarette smoke (CS) causes vessel damage and mechanism of this damage has not yet been clearly identified. Therefore, in this study we aimed to investigate whether vessel damage due to the CS exposure will be prevented by the alpha-linolenic acid (ALA) or not which has anti-inflammatory effect in mice. For this reason, mice were grouped as controls (with and without CS) and ALA (with and without CS). The CS application continued 5 days a week for two months. At the end of two months, the mice were killed by cervical dislocation and their blood and thoracic aortas were isolated. ALA Treatment increased acetylcholine relaxations. CS decreased acetylcholine relaxation. CS with ALA treatment increased acetylcholine relaxations versus just CS treatment. CS caused rising in cyclooxigenase-2 and phospholipase A2 levels. This rise is inhibited with ALA treatment. CS decreased eNOS levels. But this result was not statistically significant. Furthermore, according to electron microscopic study CS damaged both smooth muscle and endothelium. While ALA treatment prevented smooth muscle damage it didn't prevent endothelial damage. Using cigarette and CS exposure is a risk factor for cardiovascular disease. Our study showed that this disease.

Protective effect of alpha-linolenic acid on gentamicin-induced ototoxicity in mice.

Alpha-linolenic acid is one of the fatty acids known as omega 3. Previous studies have shown the antioxidant and anti-inflammatory effects of alpha-linolenic acid, which prevented cell damage by inhibiting apoptotic pathway. Also, it is known that gentamicin activates apoptotic mediators and causes necrosis in the kidney. Due to this reason, we planned a study to evaluate the protective effects of alpha-linolenic acid on gentamicin induced ototoxicity by evaluating inflammation and apoptotic mediators. For this purpose, 100 mg/kg gentamicin (i.p; intraperitoneally) and 200 mg/kg alpha-linolenic acid (gavage) are administered to mice for 9 days. On 9th and 10th days, rotarod performance was assessed to test the effect of gentamicin and alpha-linolenic acid treatment on the motor coordination of mice. Gentamicin treatment decreased fall latency of mice and gentamicin treatment together with alpha-linolenic acid increased fall latency of mice. Gentamicin treatment also increased expression of phospholipase A2(plA2), cyclooxygenase-2(COX-2) and inducible nitric oxide syntheses (iNOS). Furthermore, it increased Bax and caspase-3, which are proapoptotic proteins and decreased bcl-2 that is an antiapoptotic protein. Gentamicin treatment together alpha-linolenic acid recovered the change of expression of these enzymes. In conclusion, this study showed that alpha-linolenic acid will be useful to prevent gentamicin-induced ototoxicity by inhibiting apoptosis and inflammation.

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.

Pharmacological profile of a nitric oxide donor spermine NONOate in the mouse corpus cavernosum.

BACKGROUND/AIM: To investigate the effects of spermine NONOate in the cavernous tissue obtained from mice treated or untreated with sildenafil. MATERIALS AND METHODS: We studied the effects of spermine NONOate on the tone and nitrergic relaxation responses of isolated mouse corpus cavernosum and compared them with sodium nitroprusside in the absence or presence of L-nitroarginine, hydroxocobalamin, pyrogallol, diethyldithiocarbamate (DETCA), or 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ). The neurogenic contractions and relaxations of the tissues were induced by electrical field stimulation. Some mice received a single oral dose of sildenafil and after 1 h the effects of spermine NONOate were evaluated by in vitro studies. RESULTS: Spermine NONOate relaxed mouse corpus cavernosum in a concentration-dependent manner. Spermine-NONOate-induced relaxation was relatively slow to develop and it was reversible and reproducible. These relaxations were significantly suppressed by hydroxocobalamin, diethyldithiocarbamate, or ODQ, but not by L-nitroarginine or pyrogallol. Spermine NONOate potentiated the nitrergic relaxations to electrical field stimulation (EFS), whereas it significantly reduced EFS-induced contractions. Sildenafil treatment can enhance the relaxant responses to spermine NONOate and EFS. CONCLUSION: These findings suggest that spermine NONOate has a potent relaxant action in cavernous tissue and this effect can be potentiated by oral sildenafil treatments. Spermine NONOate may be considered an attractive treatment for erectile dysfunction in pathologic disorders with a lack of endogenous NO production.

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.

Molecular mechanism of vasorelaxant and antiatherogenic effects of the statins in the human saphenous vein graft.

In this study we aimed to investigate the vasorelaxant and antiatherogenic effects of the statins (fluvastatin and pravastatin) in the human saphenous vein grafts at the molecular level by using histopathologic, pharmacological and immunochemical techniques. The saphenous vein grafts evaluated histopathologically displayed a loss in their endothelium up to a ratio of 30% and set forth indications of functional deterioration. The pharmacological evaluations proved that the relaxation responses induced by fluvastatin and pravastatin were significantly inhibited by nitric oxide synthase inhibitor, N(G)-nitro-l-arginine, and cyclooxygenase inhibitor, indomethacin, while these responses were significantly increased by angiotensin converting enzyme inhibitors, captopril and enalapril, and rho kinase inhibitor, Y27632. The results of immunochemical studies are in accordance with the results of the pharmacological studies that the related statins increased the levels of nitric oxide, phospholipase A(2) and they decreased the levels of angiotensin II and active rho kinase. On the other hand mevalonolactone, a substrate of lipid metabolism, failed to change the effects of fluvastatin and pravastatin in the related tissue. The experimental results indicate that activation of nitric oxide synthase and phospholipase A(2)-cyclooxygenase pathway and inhibition of angiotensin converting enzyme and rho kinase may have a role on the effects of fluvastatin and pravastatin in the human saphenous vein grafts. It seems that the vasorelaxant and antiatherogenic effects of the related statins are independent of their lipid lowering mechanism.

Ethanol-induced relaxation of mouse esophagus: subcellular mechanisms.

Ethanol (164 mm) produced reproducible relaxations in isolated mouse esophageal strips. Hexamethonium (10-500 microm), a ganglionic blocking agent, and lidocaine (10-100 microm), a local anesthetic agent, failed to affect the relaxations induced by ethanol in the mouse esophagus. Although verapamil (10-500 microm), a selective blocker of L-type Ca(2+) channels, failed to affect the relaxations to ethanol, ruthenium red (10-100 microm), a selective blocker of ryanodine receptors (intracellular Ca(2+) channels), and cyclopiazonic acid (1-10 microm), a selective blocker of sarcoplasmic reticulum Ca(2+) ATPase (SERCA), significantly inhibited these relaxations. In addition, tetraethylammonium (10-100 microm), a potassium-selective ion channel blocker and N(omega)-nitro-l-arginine (l-NOARG; 10-500 microm), a specific inhibitor of nitric oxide synthase (NOS), neomycin (10-500 microm), a phospholipase C inhibitor and indomethacine (1-10 microm), a non-selective COX inhibitor, significantly inhibited the relaxations induced by ethanol. In contrast ouabain (10-100 microm), an inhibitor of Na(+)-K(+)-ATPase, failed to cause significant alteration on these relaxations in the same tissue. The results of the present study suggest that the inhibitory effect of ethanol on the mouse esophagus may be direct effect of ethanol on the muscle tissue rather than neuronal effect. In addition, intracellular but not extracellular Ca(2+) may have a role on ethanol-induced relaxations in isolated mouse esophageal strips. Potassium channels and nitric oxide may also have a role on these relaxations. Similarly, phospholypase C and arachidonic acid pathways may contribute the relaxations to ethanol. However Na(+)-K(+)-ATPase may not have a role on relaxations induced by ethanol in the mouse esophagus.

Protective effect of quercetin, a polyphenolic compound, on mouse corpus cavernosum.

Flavonoids are plant-based phenolic compounds, and quercetin is the most abundant dietary member of this family. One of the most important characteristics of quercetin is its antioxidant property. The aim of this study was to investigate antioxidant effects of quercetin on corpora cavernosa of mice. Corpora cavernosa were isolated in organ baths, precontracted with phenylephrine (0.5 microm) and relaxant responses were mediated by acetylcholine (0.1-1 microm), electrical field stimulation (EFS, 1-16 Hz, 0.5 ms, 30 V) or acidified sodium nitrite (a NaNO(2), 0.5 mm). Superoxide anion generators; pyrogallol (50 microm), hydroquinone (100 microm), LY 83583 (6-Anilinoquinolin-5,8-quinone, 10 microm) and superoxide dismutase (SOD) inhibitor; diethyldithiocarbamic acid (DETCA, 8 mm) were used in order to expose corpus cavernosa to oxidant stress. Acetylcholine (0.1-1 microm) induced relaxant responses were significantly inhibited in LY 83583 (10 microm) and DETCA + LY 83583 applicated trials. EFS-induced relaxant responses were significantly inhibited in DETCA (8 mm) and DETCA + LY 83583 administrated trials. On the other hand, acidified sodium nitrite-induced responses were inhibited by all of the superoxide anion generators tested. Quercetin (10 microm) failed to improve the inhibitions on endothelium and electrically stimulated responses. Acidified sodium nitrite (0.5 mm) mediated relaxant responses were significantly restored by quercetin except the groups in which LY 83583 were used. The data suggest that quercetin acts as a protective agent in mouse corpus cavernosum, increasing the bioavailability of exogenous nitric oxide by protecting it from superoxide anion (O(2)(-)).

The impact of extracellular and intracellular Ca2+ on ethanol-induced smooth muscle contraction.

AIM: To evaluate the impact of extracellular and intracellular Ca2+ on contractions induced by ethanol in smooth muscle. METHODS: Longitudinal smooth muscle strips were prepared from the gastric fundi of mice. The contractions of smooth muscle strips were recorded with an isometric force displacement transducer. RESULTS: Ethanol (164 mmol/L) produced reproducible contractions in isolated gastric fundal strips of mice. Although lidocaine (50 and 100 micromol/L), a local anesthetic agent, and hexamethonium (100 and 500 micromol/L), a ganglionic blocking agent, failed to affect these contractions, verapamil (1-50 micromol/L) and nifedipine (1-50 micromol/L), selective blockers of L-type Ca2+ channels, significantly inhibited the contractile responses of ethanol. Using a Ca(2+)-free medium nearly eliminated these contractions in the same tissue. Ryanodine (1-50 micromol/L) and ruthenium red (10-100 micromol/L), selective blockers of intracellular Ca2+ channels/ryanodine receptors; cyclopiazonic acid (CPA; 1-10 mumol/L), a selective inhibitor of sarcoplasmic reticulum (SR) Ca(2+)-ATPase; and caffeine (0.5-5 mmol/L), a depleting agent of intracellular Ca2+ stores, significantly inhibited the contractile responses induced by ethanol. In addition, the combination of caffeine (5 mmol/L) plus CPA (10 micromol/L), and ryanodine (10 micromol/L) plus CPA (10 micromol/L), caused further inhibition of contractions in response to ethanol. This inhibition was significantly different from those associated with caffeine, ryanodine or CPA. Furthermore the combination of caffeine (5 mmol/L), ryanodine (10 micromol/L) and CPA(10 micromol/L) eliminated the contractions induced by ethanol in isolated gastric fundal strips of mice. CONCLUSION: Both extracellular and intracellular Ca2+ may have important roles in regulating contractions induced by ethanol in the mouse gastric fundus.

Molecular mechanism of KCl-induced relaxation of the esophagus.

KCl (40 mM) caused reproducible relaxations in frog esophagus. N(G)-nitro-L-arginine (L-NOARG; 1-100 microM), a steriospecific inhibitor of nitric oxide synthase (NOS), completely inhibited the relaxations induced by KCl but not those induced by vasoactive intestinal polypeptide (VIP) antagonist. The inhibitory effect of L-NOARG was prevented by L-arginine (L-ARG; 0.1-1 mM), the precursor of nitric oxide (NO) biosynthesis, but not by D-arginine (D-ARG; 0.1-0.5 mM), the enantiomer of L-arginine. L-ARG or D-ARG alone did not significantly modify the effect of KCl. The relaxations to KCl were significantly inhibited by omega conotoxin (omega-conotoxin; 0.1 microM), a selective blocker of N-type calcium channels. Propranolol (0.1-1 microM), a nonselective blocker of beta-adrenergic receptors, prazosine (0.01-0.1 microM), a selective blocker of alpha(1)-adrenergic receptors, phentolamine (0.1-1 microM), a nonselective blocker of adrenergic receptors, atropine, a selective blocker of muscarinic cholinergic receptors, and lidocaine (1-10 microM), a blocker of sodium channels, had no effect on KCl-evoked relaxations. Caffeine (500 microM), an intracellular calcium releasing agent, did not significantly modify the effect of KCl. In contrast, ruthenium red (100 microM), a selective blocker of ryanodine receptors (intracellular Ca(2+) channels), significantly inhibited these relaxations. Similarly, potassium channel blockers such as 4-aminopyridine (4-AP; 100 microM) and tetraethylammonium (TEA; 100 microM) caused a significant inhibition on relaxations to KCl. In addition, ouabain (100 microM), a specific blocker of Na(+)-K(+)-ATPase, also caused a significant inhibition on these relaxations. The results suggest that NO, Na(+)-K(+)-ATPase and potassium channels may have a role on relaxations induced by 40 mM KCl in the frog esophagus.

Urocortin induces endothelium-dependent vasodilatation and hyperpolarization of rat mesenteric arteries by activating Ca2+-activated K+ channels.

Urocortin, a member of corticotropin releasing factor (CRF) peptide family, has positive chronotropic and inotropic effects on heart and also shows a vasodilatory effect. However, the mechanism underlying its vasodilatory effect has yet to be elucidated. Endothelium-dependent relaxation of resistance arteries is mainly achieved by activation of K+ channels. Therefore, we investigated possible role of K+ channels and hyperpolarization for the vasodilatory effect of urocortin using the isolated perfused rat mesenteric arteries. Urocortin (0.2 nM) produced a slow-onset decrease in the perfusion pressure of the mesenteric vascular bed, which was elevated by an alpha1-adrenoceptor agonist, phenylephrine (2-4 microM). Urocortin also hyperpolarized the main mesenteric artery. Removal of endothelium with saponin treatment considerably inhibited the relaxation and hyperpolarization induced by urocortin. In contrast, the hyperpolarization was not significantly changed by cyclooxygenase inhibitor, indomethacin (1 microM) and/or nitric oxide synthase inhibitor, N(omega)-nitro-L-arginine (100 microM). Urocortin-induced relaxation was not affected by the combination of a guanylyl cyclase inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 1 microM), indomethacin and N(omega)-nitro-L-arginine. However, the relaxation and hyperpolarization were abolished by high extracellular potassium concentration (40 mM) or by a large conductance Ca(2+)-activated K+ channel blocker, charybdotoxin (1 nM). Glibenclamide (1 microM), an ATP-dependent K+ channel inhibitor, did not affect the relaxation and hyperpolarization. These results suggest that urocortin causes endothelium-dependent relaxation and hyperpolarization of rat mesenteric arteries, probably through the activation of charybdotoxin sensitive Ca2+-activated K+ channels. These findings also indicate an essential role of the endothelium for the urocortin-elicited vascular relaxation and hyperpolarization.

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 alpha1-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 alpha2-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 alpha,beta-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 intake on the impaired renal vascular responses in the gentamicin-treated rats.

The purpose of this study was to investigate the effect of gentamicin (100 mg/kg/day, i.p.) treatment on endothelium-dependent and -independent vasodilation in isolated perfused rat kidney, and the effect of amino acid L-arginine (in the drinking water, 2.25 g/l) on renal dysfunction induced by gentamicin. When gentamicin-treated groups were compared with the control group, it was observed that BUN and creatinine levels increased significantly. Also, the relaxant responses induced by acetylcholine, sodium nitroprusside and pinacidil decreased. Histopathological examination indicated acute tubular necrosis in this group. In animals treated with gentamicin together with L-arginine, there was a significant amelioration in the BUN and creatinine levels. The vasodilator responses were similar to those of the control group. Histopathological examination indicated only hydropic degeneration in tubular epithelium of kidney. Co-administration of L-NG-nitroarginine methyl ester (L-NAME) (112.5 mg/l), an inhibitor of nitric oxide synthase, and L-arginine to rats treated with gentamicin did not change the protective effect of L-arginine. In rats receiving L-NAME alone, the level of BUN and creatinine and vasodilation to acetylcholine were not significantly different when compared to those of the control group, while relaxant responses to sodium nitroprusside and pinacidil were increased. These results suggest that gentamicin leads to an impairment in vascular smooth muscle relaxation in addition to acute tubular necrosis in the rat kidney. Supplementation of L-arginine has an important protective effect on gentamicin-induced nephropathy.

Rho-kinase expression and its contribution to the control of perfusion pressure in the isolated rat mesenteric vascular bed.

Rho-kinase expression was investigated in the rat mesenteric artery and the effects of its inhibitors, (+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl) cyclohexanecarboxamide dihydrochloride monohydrate (Y-27632) and fasudil (HA-1077), were examined on the increase in perfusion pressure induced by two different receptor agonists, namely the alpha-adrenoceptor agonist, phenylephrine and, the endothelin ET(A) and ET(B) receptor agonist, endothelin-1. Y-27632 and fasudil produced a concentration-dependent decrease in perfusion pressure. There was no difference between the concentration-response lines of these two inhibitors. The maximum decrease in the perfusion pressure induced by 10(-5) M Y-27632 was 85.8+/-3.7% when the tone was increased by phenylephrine. However, it was 48.1+/-5.4% (P<0.001) when the perfusion pressure was elevated by endothelin-1. Saponin perfusion (100 mg l(-1), for 10 min), which abolished acetylcholine-induced relaxation, did not significantly modify the Y-27632-elicited relaxation. Western blot analysis revealed that rat mesenteric artery expresses Rho-kinase protein with a molecular weight of approximately 160 kDa. These results show that Rho-kinase enzyme is expressed in rat mesenteric artery and that it contributes to the control of vascular resistance. Moreover, endothelium removal had no marked effect on the vasodilatation induced by Y-27632. In addition, the endothelin-1-induced vasoconstriction was more resistant to the Rho-kinase inhibitors than was that induced by phenylephrine, probably because excitatory endothelin receptors are associated with this signal transduction pathway at a different level from that of alpha-adrenoceptors.

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.

Effects of chronic cadmium exposure on contractility of the rat detrusor.

The chronic effects of Cd2+ on the myogenic contractions induced by acetylcholine (ACh), and the neurogenic contractions induced by electrical field stimulation (EFS) of the rat detrusor were investigated. Wistar Kyoto rats weighing 150-250 g were randomly divided into four groups each containing ten animals. Three groups received intraperitoneal Cd2+ (0.25, 0.5 and 1 mg/kg, respectively) dissolved in saline twice a week for 3 months. The control group received only saline (0.3 ml). At the end of 3 months, the urinary bladders were surgically removed and a strip of detrusor was prepared from each bladder. An atomic absorption device and the standard addition method were used to determine blood levels of Cd2+ and the Cd2+ levels of the remaining parts of each bladder. The responses of the detrusor strips were studied in organ chambers. The tissues were first treated with ACh and then with EFS. The responses were recorded by isotonic transducers. The tissue Cd2+ levels were significantly increased in the Cd2+ treated rats in a dose-dependent manner except in the 0.25 mg/kg Cd2+ treated group. ACh-induced contractions were significantly attenuated only in the 1 mg/ kg Cd2+ treated rats. The contractions induced by EFS were significantly decreased in all of the Cd2+-treated groups. but there were no significant differences between the groups. This study showed that Cd2+ exposure for 3 months impairs neurogenic and myogenic contractile activity in the rat detrusor muscle. This action seems to be at least partly due to an inhibition of the cholinergic muscarinic system. This may have clinical implications for people who are exposed to Cd2+.