Melatonin treatment protects against diabetes-induced functional and biochemical changes in rat aorta and corpus cavernosum

Enhanced oxidative stress due to diabetes is accepted to lead to endothelial dysfunction, and this is known to play a key role in the pathogenesis of diabetic vascular diseases and complications. This study was designed to determine the possible protective effect of melatonin and/or insulin treatment on the functional and biochemical changes caused by hyperglycemia in aorta and corpus cavernosum of diabetic rats. Wistar albino male rats were rendered diabetic by injecting streptozotocin (60 mg/kg, intraperitoneally (i.p.)). Melatonin (10 mg/kg, i.p.) and/or insulin (6 U/kg, subcutaneously (s.c.)) were administered for 8 weeks. In the diabetic group, the contractile responses of aortic strips to phenylephrine were significantly impaired (EC(50) 5.5 x 10(-7) M in diabetic and EC(50) 1.47 x 10(-7) M in the control group, P<0.001). Treatment with melatonin (EC(50) 4.6 x 10(-7) M) or insulin+melatonin (EC(50) 1.68 x 10(-7) M, P<0.001) improved the contractile responses. Acetylcholine caused a dose-dependent relaxation response (EC(50) 1.58 x 10(-7) M) which was impaired in the diabetic group (EC(50) 26 x 10(-7) M, P<0.001). There was less impairment in melatonin-, insulin- and insulin+melatonin-treated groups (EC(50) 11.61 x 10(-7), 7.3 x 10(-7) and 1.41 x 10(-7) M, respectively, P<0.01). Contractile responses to phenylephrine were also impaired in the corpus cavernosum strips (EC(50) 2.06 x 10(-5) M in diabetic and 0.94 x 10(-5) M in the control group, P<0.001). In the melatonin- (EC(50) 1.59 x 10(-5) M) and insulin+melatonin-treated (EC(50) 1.53 x 10(-5) M, P<0.5) groups contractile responses were improved. In the diabetic group, the relaxation responses of corpus cavernosum strips to acetylcholine were impaired (EC(50) 24.12 x 10(-5) M, P<0.001), and treatment with melatonin (EC(50) 0.68 x 10(-5) M), insulin (EC(50) 0.53 x 10(-5) M) or insulin+melatonin (0.98 x 10(-5) M, P<0.001) restored the responses to acetylcholine. In diabetic tissues, malondialdehyde levels were increased while glutathione levels were decreased, demonstrating oxidative damage. This was also prevented by treatment with melatonin or the melatonin and insulin combination. The diabetic state enhances the generation of free radicals, and both melatonin and insulin treatments reduced this oxidative stress; however, treatment with the combination was the most efficient in preventing diabetes-induced damage. Thus, our results suggested that giving diabetic patients adjuvant therapy with melatonin may have some benefit in controlling diabetic complications.     

Role of opioid and nitric oxide systems in the nonadrenergic noncholinergic-mediated relaxation of corpus cavernosum in bile duct-ligated rats

Changes in nonadrenergic noncholinergic (NANC)-mediated relaxation of the anococcygeus muscle have been demonstrated in cholestasis. Cholestasis is also associated with accumulation of endogenous opioid peptides and nitric oxide (NO) overproduction. This study was therefore undertaken to investigate the effect of cholestasis on the NANC-mediated relaxation of corpus cavernosum in bile duct-ligated rats and to examine the possible roles of the opioid system and nitric oxide in the cholestasis-associated alterations of corpus relaxation. Bile duct-ligated and sham-operated rats were treated for 2 weeks with either normal saline, N (omega)-nitro L-arginine methylester (L-NAME) (3 mg/kg/day, i.p.) or naltrexone (20 mg/kg/day, i.p.). On the 14th day, the strips of corpus cavernosum were mounted under tension in a standard oxygenated organ bath with guanethidine sulfate (5 microM) and atropine sulfate (1 microM) (to produce adrenergic and cholinergic blockade). The strips were precontracted with phenylephrine hydrochloride (7.5 microM) and electrical field stimulation was applied at different frequencies to obtain NANC-mediated frequency-dependent relaxant responses. The results showed that the amplitudes of relaxation responses at each frequency in bile duct-ligated rats were greater than the responses of sham-operated animals. This increase in relaxation responses in bile duct-ligated rats was inhibited by chronic L-NAME administration for 2 weeks so it seemed that it might be due to the nitric oxide overproduction in cholestatic states. Chronic administration of naltrexone for 2 weeks to bile duct-ligated rats had the same inhibitory effect on the relaxation responses. Our results demonstrated that in cholestasis, there was an increase in NANC-mediated relaxation of corpus cavernosum and both opioid and nitric oxide systems were involved in this increase.     

Enzyme activities of the nitric oxide-cGMP pathway in corpus cavernosum isolated from middle-aged rats

Cyclic guanosine-3',5'-monophosphate (cGMP)-mediated mechanisms play an important role in vasodilation and blood pressure regulation. We investigated basal activity of the nitric oxide (NO)-cGMP signal transduction pathway in corpus cavernosum from both middle-aged and young rats, and the electrical field stimulation-induced relaxation in the organ was also evaluated. In middle-aged rats, nitric oxide synthase (NOS) and cGMP-phosphodiesterase activities were significantly decreased; however, guanylate cyclase activity was similar. cGMP concentration, a secondary messenger of NO, remained almost the same level as compared with young rats. These results suggest that decrease in cGMP-phosphodiesterase activity is likely to account for the maintenance of cGMP concentration. In isolated corpus cavernosum from middle-aged rats, electrical field stimulation-induced relaxation was partially impaired. These results suggest that downregulation of the NOS and cGMP-phosphodiesterase activities are early events in the pathogenesis of erectile dysfunction.     

Chronic administration of fluoxetine impairs neurogenic and endothelium-dependent relaxation of the rabbit corpus cavernosum smooth muscle

Antidepressants, including selective serotonin reuptake inhibitors (SSRIs), cause erectile dysfunction; however, the mechanism by which they cause erectile function is unclear. We investigated the reactivity of the corpus cavernosum after chronic fluoxetine treatment in rabbits. Twelve rabbits were randomly divided into two groups: control (n = 6) or 20 mg/kg/day of fluoxetine delivered i.p. (n = 6). The reactivity of the corpus cavernosum tissue from the fluoxetine-treated and control groups was studied in organ chambers after 21 days of fluoxetine injection. In the fluoxetine-treated group, endothelium-dependent relaxation of the corpus cavernosum in response to acetylcholine was significantly decreased compared to the control group. However, the sensitivity (i.e., pD₂) of the fluoxetine-treated cavernosal tissue strips to acetylcholine was not changed with respect to controls. Electrical field stimulation (EFS)-induced neurogenic relaxation was also significantly reduced in the fluoxetine-treated group. Relaxation in response to the nitric oxide (NO) donor sodium nitroprusside was similar between the cavernosal tissues from the two groups. There was also no change in agonist potency between the two groups. Additionally, chronic fluoxetine treatment had no effect on KCl-induced contractile responses. When tissue contraction was produced with phenylephrine to study relaxation in response to various stimuli, the tension induced was similar between the fluoxetine-treated and control groups. This study suggests that chronic fluoxetine treatment causes significant functional changes to the penile erectile tissue of rabbits, and these changes may contribute to the development of impotence.     

Effects of the Rho-kinase inhibitors,Y-27632 and fasudil,on the corpus cavernosum from diabetic mice

Relaxant responses to two Rho-kinase inhibitors, (+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl) cyclohexanecarboxamide dihydrochloride monohydrate (Y-27632) and fasudil, were compared in the corpus cavernosum obtained from diabetic and non-diabetic mice. Streptozotocin (100 mg kg(-1) day(-1), for 2 days) induced diabetes with a blood glucose level of 318+/-55.4 mg dl(-1); whereas it was 85.4+/-4.1 mg dl(-1) in control mice (P<0.05). Electrical field stimulation (40 V, 0.5 ms, 1, 2, 4, 8, 16 Hz for 15 s) and acetylcholine-induced relaxations were markedly attenuated in the corpus cavernosum from streptozotocin-diabetic mice whereas responses to Y-27632 (10(-9)-3 x 10(-5) M) and fasudil (10(-9)-3 x 10(-5) M) were not altered. EC(50) values for Y-27632 were 2.98+/-0.89 and 4.19+/-2.71 microM in the corpus cavernosum from control and diabetic mice, respectively (P>0.05). The values for fasudil were 7.42+/-4.91 and 3.53+/-1.41 microM in the corpus cavernosum from control and diabetic mice, respectively (P>0.05). These results may suggest that, in diabetes, the relaxant effects of the Rho-kinase inhibitors may not be changed and thus, they may have a beneficial therapeutic effect in diabetic erectile dysfunction.     

Relaxing effects induced by the soluble guanylyl cyclase stimulator BAY 41-2272 in human and rabbit corpus cavernosum

5-Cyclopropyl-2-[1-(2-fluoro-benzyl)-1H-pyrazolo[3,4-b]pyridin-3-yl]-pyrimidin-4-ylamine (BAY 41-2272) is a potent soluble guanylyl cyclase stimulator in a nitric oxide (NO)-independent manner. The relaxant effect of BAY 41-2272 was investigated in rabbit and human corpus cavernosum in vitro. BAY 41-2272 (0.01-10 microM) relaxed both rabbit (pEC(50)=6.82+/-0.06) and human (pEC(50)=6.12+/-0.10) precontracted cavernosal strips. The guanylyl cyclase inhibitor (ODQ, 10 microM) caused significant rightward shifts in the concentration-response curves for BAY 41-2272 in rabbit (4.7-fold) and human (2.3-fold) tissues. The NO synthesis inhibitor (N-nitro-L-arginine methyl ester (L-NAME), 100 microM) also produced similar rightward shifts, revealing that BAY 41-2272 acts synergistically with endogenous NO to elicit its relaxant effect. The results also indicate that ODQ is selective for the NO-stimulated enzyme, since relaxations evoked by BAY 41-2272 were only partly attenuated by ODQ. The present study shows that both BAY 41-2272 and sildenafil evoke relaxations independent of inhibition of haem in soluble guanylate cyclase. Moreover, there is no synergistic effect of the two compounds in corpus cavernosum.     

洛土辛对心肌及阴茎海绵体环核苷酸含量和收缩功能的影响

目的　研究洛土辛 (Lot)对磷酸二酯酶 (PDE)Ⅲ或Ⅴ亚型的抑制作用及选择性。方法　采用放射免疫测定法及收缩张力记录。结果　Lot和氨力农(Amr)剂量依赖性地增加大鼠心肌cAMP含量 ,且Lot的作用强于Amr。在家兔阴茎海绵体 ,Lot和扎普司特 (Zap)可剂量依赖性地增加海绵体cGMP含量 ,Lot的作用远弱于Zap。Lot,罂粟碱 (Pap)、Zap及Amr可显著抑制预先用苯肾上腺素诱发的阴茎海绵体血管收缩 ,其EC50 分别依次为Zap >Pap >Amr >Lot。结论　提示洛土辛的作用机理可能与选择性的抑制PDEⅢ有关。     

Xanthine‐analog,KMUP‐2, enhances cyclic GMP and K+ channel activities in rabbit aorta and corpus cavernosum with associated penile erection

The pharmacological properties of KMUP‐2 were examined in isolated rabbit aorta and corpus cavernosum smooth muscle (CCSM). KMUP‐2 caused relaxations that were attenuated by removed endothelium, high K⁺, and pretreatment with the soluble guanylate cyclase (sGC) inhibitors methylene blue (10 μM) and ODQ (1 μM), a NOS inhibitor, L‐NAME (100 μM), a K⁺ channel blocker TEA (10 mM), a K_ATP channel blocker glibenclamide (1 μM), a voltage‐dependent K⁺ channel blocker 4‐AP (100 μM), and the Ca²⁺‐dependent K⁺ channel blockers apamin (1 μM) and charybdotoxin (ChTX, 0.1 μM). The relaxant responses of KMUP‐2 (0.01, 0.05, 0.1 μM) together with a PDE inhibitor, IBMX (0.5 μM), had additive effects on rabbit aorta and CCSM. Additionally, KMUP‐2 (100 μM) also affected cGMP metabolism, due to its inhibiting activity on PDE in human platelets. KMUP‐2 (0.1–100 μM) further induced an increase of intracellular cGMP levels in the primary cultured rabbit aortic and CCSM cells. These increases in cGMP content were abolished in the presence of methylene blue (100 μM) and ODQ (10 μM). Obviously, the relaxant effects of KMUP‐2 on rabbit isolated tissues are more sensitive in CCSM than in aorta. Moreover, KMUP‐2 also stimulated NO/sGC/cGMP pathway and subsequent elevation of cGMP by blockade of PDE and enhanced opening of K⁺ channels in rabbit aorta and CCSM. KMUP‐2 (0.2, 0.4, 0.6 mg/kg), similar to KMUP‐1 and sildenafil, caused increases of intracavernous pressure (ICP) and duration of tumescene (DT) in a dose‐dependent manner. It is concluded that both the increases of cGMP and the opening activity of K⁺ channels play prominent roles in KMUP‐2‐induced aortic smooth muscle and CCSM relaxation and increases of ICP in rabbits. Drug Dev. Res. 55:162–172, 2002. © 2002 Wiley‐Liss, Inc.     

Exposure to low doses of malathion during juvenile and peripubertal periods impairs testicular and sperm parameters in rats: Role of oxidative stress and testosterone

Malathion is an organophosphate insecticide used in agriculture and for controlling vector-borne diseases such as Zika. Humans can be exposed to malathion by means of ingestion of contaminated food. The juvenile and peripubertal periods are a large window of vulnerability to the action of toxic agents. The aim of the present study was to evaluate the effects of low doses of malathion during the development of testes in the juvenile and peripubertal periods in rats. For this purpose, 45 male Wistar rats (postnatal day (PND) 25) were assigned to 3 experimental groups and treated for 40 days. The animals were exposed daily to malathion 10 mg/kg (M10 group) or 50 mg/kg (M50 group) diluted in 0.9 % saline via gavage. The control group received only the vehicle. On the 40th experimental day, the rats were anaesthetized and euthanized. The blood was collected for determination of testosterone concentration. The testes were removed and weighed. Spermatozoa from the vas deferens were used for sperm morphological analysis. The testes were used for evaluation of sperm count and oxidative stress status to determine the inflammatory profile and analysis of tissue constitution. The results showed that both malathion doses reduced the sperm count and increased the number of abnormal sperms. Furthermore, both doses altered the spermatogenetic process, delayed spermiogenesis, reduced the Leydig and Sertoli cell number and increased the thickness of tunica albuginea. The M10 group presented increased IL-10 levels and reduced GSH levels. These parameters did not change in the M50 group. However, the M50 group showed an increase in the number of abnormal seminiferous tubules, a decrease in plasma testosterone concentration and an increase in lipid peroxidation in the testes. In conclusion, the exposure to low doses of malathion during juvenile and peripubertal development resulted in testicular toxicity and compromised the testicular morphology and function.     

Small and intermediate conductance Ca<Superscript>2+</Superscript>-activated K<Superscript>+</Superscript> channels confer distinctive patterns of distribution in human tissues and differential cellular localisation in the colon and corpus cavernosum

The SK/IK family of small and intermediate conductance calcium-activated potassium channels contains four members, SK1, SK2, SK3 and IK1, and is important for the regulation of a variety of neuronal and non-neuronal functions. In this study we have analysed the distribution of these channels in human tissues and their cellular localisation in samples of colon and corpus cavernosum. SK1 mRNA was detected almost exclusively in neuronal tissues. SK2 mRNA distribution was restricted but more widespread than SK1, and was detected in adrenal gland, brain, prostate, bladder, liver and heart. SK3 mRNA was detected in almost every tissue examined. It was highly expressed in brain and in smooth muscle-rich tissues including the clitoris and the corpus cavernosum, and expression in the corpus cavernosum was upregulated up to 5-fold in patients undergoing sex-change operations. IK1 mRNA was present in surface-rich, secretory and inflammatory cell-rich tissues, highest in the trachea, prostate, placenta and salivary glands. In detailed immunohistochemical studies of the colon and the corpus cavernosum, SK1-like immunoreactivity was observed in the enteric neurons. SK3-like immunoreactivity was observed strongly in smooth muscle and vascular endothelium. IK1-like immunoreactivity was mainly observed in inflammatory cells and enteric neurons of the colon, but absent in corpus cavernosum. These distinctive patterns of distribution suggest that these channels are likely to have different biological functions and could be specifically targeted for a number of human diseases, such as irritable bowel syndrome, hypertension and erectile dysfunction.Abbreviations SK/IK/BK Small/intermediate/big conductance calcium-activated potassium channels respectively - AHP Afterhyperpolarisation - EBIO 1-ethyl-2-benzimidazolone - PCR Polymerase chain reaction - CNS Central nervous system     

Ethambutol induces testicular damage and decreases the sperm functional competence in Swiss albino mice

The present study reports the effect of ethambutol (EMB) on testicular function. Prepubertal and adult male Swiss albino mice were treated with 40, 80, 160 mg/kg body weight of EMB, intraperitoneally, every alternate day for 4 weeks. After 2 weeks gap, mice were sacrificed to collect caudal spermatozoa. EMB treatment resulted in a dose-dependent decrease in the testicular weight, sperm count and motility while the percentage of sperm with head abnormalities, immature chromatin (P < 0.001) and DNA damage increased (P < 0.01). In addition, EMB treatment resulted in significant depletion of glutathione (P < 0.05–P < 0.01) and histopathological abnormalities such as large cells, vacuolation of tubules and isolated colonies of spermatogenic cells were observed. Oct4, 17β-Hsd and c-Kit mRNA was marginally elevated in EMB treated testes at the highest dose studied. In conclusion, the result of the present study indicates that EMB has adverse effect on testicular function and impairs the sperm functional competence.     

Sulfur dioxide inhalation lowers sperm quality and alters testicular histology via increasing expression of CREM and ACT proteins in rat testes

Sulfur dioxide (SO₂) is one of the main atmospheric pollutants worldwide, and is reported to be responsible for the formation of severe haze in China. Some studies have demonstrated a potential harmful effect of SO₂ on the male reproductive system; however the underlying mechanism is still unknown. The purpose of this study is to investigate the roles of cytochrome P450 (P450), cAMP-responsive element modulator (CREM), and activator of CREM (ACT) in SO₂-induced toxicity. Forty-eight male Wistar rats were randomly divided into an experimental and control group. The experiment group was exposed to SO₂ in ambient air (10 ppm, 4 h/day), and the control group was treated with filtered air in the same conditions. After 2 weeks, the results showed a significant decrease in body weight and sperm motility, and an increase in the testis weight-to-body weight ratio as compared to the control group. Histological investigation suggested that SO₂ exposure led to loose arrangement of the spermatogenic cells and local structural damage in the seminiferous tubules. Moreover, the expressions of P450, CREM and ACT proteins increased in the testes by 0.22%, 47.26% and 23.38%, respectively. Taken together, SO₂ inhalation lowered sperm quality, altered testicular histology, and increased expressions of CREM and ACT proteins in the testes of rats. Overall, these results could contribute to a better understanding of SO₂-induced male reproductive toxicity.     

MDMA (ecstasy) delays pubertal development and alters sperm quality after developmental exposure in the rat

3,4-Methylenedioxymethamphetamine, MDMA or “ecstasy” is consumed mainly by young population at childbearing age. Therefore, there may be a risk of exposure of some pregnant women. The effects of the developmental exposure to MDMA on the sexual development and long-term sexual behaviour/fertility were assessed in Sprague–Dawley rats. MDMA was administered subcutaneously at 0 (control), 0.5, 5 and 10 mg/kg to female rats once a day, three consecutive days a week during 10 weeks, including gestation and lactation. The male offspring was evaluated for sexual maturation and mated with untreated sexually receptive females to evaluate the mating and pregnancy rates. Hormonal, haematological, biochemical, histological, genotoxicological and testicular and sperm parameters were also evaluated. A significant higher incidence of DNA damage in sperm and interstitial oedema in testes was found. There was also a significant and dose-related decrease in sperm count and a significant decrease in sperm motility at all doses. A significant delay in preputial separation onset in all treated groups was observed. This study reports by the first time an alteration of spermatogenesis after in utero and lactation MDMA exposure in the rat.     

The effect of testosterone and of castration on anococcygeus muscle contractility and on plasma corticosterone levels in the rat

The effect of testosterone and of castration on the contractility of the rat anococcygeus muscle, on plasma corticosterone concentrations, and on adrenal gland weights, was investigated. Castration was without effect on smooth muscle reactivity. However, testosterone increased muscle contractility to both NA and ACh, when given to control or castrated rats. Castration reduced both plasma corticosterone and adrenal gland weight, and this effect could be reversed by testosterone. It is concluded that changes in circulatind testosterone levels cannot explain the lack of effect of adrenalectomy on muscle contractility. The possible mechanism of action of testosterone is discussed.     

Embryonic exposure to octylphenol induces changes in testosterone levels and disrupts reproductive efficiency in rats at their adulthood

The purpose of the present study was to investigate the effects of prenatal exposure to octylphenol (OP) at the dose of 50 mg/kg body weight on days 1, 7 and 14 of pregnancy on reproductive health of male rats at adulthood. F1 male rats from control and OP exposed animals were weaned and maintained up to postnatal day (PND) 100. The indices of testis, epididymis and seminal vesicles were significantly decreased in male rats exposed to OP during embryonic development when compared with controls. Significant reduction in the epididymal sperm count, viable sperms and motile sperms and number of tail coiled sperms (HOS-test) were observed in experimental rats when compared to control rats. The levels of serum testosterone and also activity levels of testicular hydroxysteroid dehydrogenases were significantly decreased with a significant increase in the serum follicle stimulating and leutinizing hormones in experimental rats. Furthermore, embryonic exposure to OP caused significant down regulation of StAR, 3ß hydroxysteroid dehydrogenase and 17ß hydroxysteroid dehydrogenase mRNAs in testis of adult rats as compared to control rats. The results of fertility studies revealed that there was an increase in the mating index in experimental rats with an increase in the pre- and post-implantation losses in rats cohabited with treated animals indicating poor male reproductive performance.     

Paint thinner exposure inhibits testosterone synthesis and secretion in a reversible manner in the rat

Occupational exposure and sniffing of toluene-based organic solvents is an important public health problem. In this study, we have investigated the effects of paint thinner inhalation on testosterone synthesis and secretion in the male rat. A control group inhaled normal air ventilation. The remaining animals were divided into three groups and exposed to paint thinner in a glassy cage for 15 and 30 days (2 h/day). A group of rats was allowed to recover for 15 days after 30 days of exposure. Toluene concentration (the largest constituent in thinner, 66%) was set at 1500 ppm in the inhaled air. At the end, all animals were decapitated and blood samples obtained. Testes and seminal vesicles were removed and weighed out. Serum total testosterone levels were determined by chemiluminescence enzyme immunoassay. Testicular tissue specimens were processed for semi-quantitative evaluation of immunohistochemical testosterone staining and light microscopy. Intensity of immunostaining was evaluated on a scale between 0 (no staining), 1 (minimal), 2 (mild), 3 (moderate) and 4 (strong staining). Serum testosterone levels (ng/ml) were decreased by 15-day (3.31 ± 0.61) and 30-day (1.17 ± 0.54, p < 0.02) thinner exposure compared to the controls (3.91 ± 1.03). Another group of rats exposed to thinner for 30 days and then allowed to recover for a period of 15 days had significantly elevated levels of testosterone values (3.77 ± 1.1; p < 0.05). Immunohistochemical testosterone staining of the cytoplasm of Leydig cells was moderate (3+) and mild (2+) in 15 and 30 days thinner inhalation groups, respectively. Strong staining (4+) was restored following the recovery period. Testicular weight was significantly reduced in all test groups compared to the control values (p < 0.01). Diameters of seminiferous tubules were significantly decreased in the solvent exposed groups with enlarged connective tissue. The present findings suggest that paint thinner inhalation inhibits testosterone synthesis and secretion by a direct action on the Leydig cells in a reversible manner.     

An in vitro study on reproductive toxicity of aluminium chloride on rabbit sperm: the protective role of some antioxidants

An in vitro study using rabbit sperm was designed to evaluate the cytotoxic effects of different concentrations of aluminium chloride (AlCl(3)) at 0, 2 and 4h of incubation on sperm motility and viability, oxidative status and the activities of some antioxidant enzymes (superoxide dismutase (SOD) and catalase (CAT)), transaminases and acid phosphatase. The role of vitamin C (1 mM) or vitamin E (2 mM) was also investigated in counteracting deterioration caused by AlCl(3) on the tested parameters. Rabbit sperm was incubated with different concentrations of AlCl(3) (0, 1, 5, 10, 15 and 20 mM) with or without vitamin C or vitamin E for 2 and 4 h. Results revealed that the percentage of motile and viable sperm decreased significantly after AlCl(3) treatment at 10, 15 and 20 mM and the response was both concentration and time dependent. Aluminium chloride at concentrations of 10, 15 and 20 mM caused significant induction of oxidative stress as evidenced by increased thiobarbituric acid reactive substances (TBARS) levels and inhibition in the activities of SOD and CAT. Increase in the activities of aspartate transaminase (AST) and alanine transaminase (ALT) and decline in the activity of acid phosphatase (ACP) were also observed at AlCl(3) concentrations of 15 and 20 mM. Co-incubation with either vitamin C or vitamin E resulted in marked degrees of protection against AlCl(3)-induced cytotoxic effects, represented in decreased TBARS levels and restoration of enzymes activities near control. On the other hand, no significant effect was exerted from vitamin C or vitamin E on motility and viability. The present study demonstrated that AlCl(3) caused deterioration in sperm motility and viability, enhancement of free radicals and alterations in enzymes activities. The antioxidants revealed protective effects against the cytotoxicity of AlCl(3).     

Influence of the endothelium on ex vivo tolerance and metabolism of glyceryl trinitrate in rat aorta

The influence of the endothelium on glyceryl trinitrate metabolism and relaxation and the relationship to tolerance induced by transdermal glyceryl trinitrate was explored in rat aorta. Metabolism was assessed in artery segments incubated with glyceryl trinitrate (1.0 microM) for 2 min and the contents of 1,2- and 1,3-glyceryl dinitrate measured by gas chromatography. In non-tolerant arteries mean contents of glyceryl trinitrate, 1,2-glyceryl dinitrate and 1,3-glyceryl dinitrate were 3.2, 0.23 and 0.10 nmol/g, respectively; in tolerant arteries the content of 1,2-glyceryl dinitrate was reduced by approximately 60%. Endothelium removal or nitric oxide synthase (NOS) inhibition did not affect metabolite contents but increased the relaxant response to glyceryl trinitrate in the tolerant artery to an extent that tolerance was significantly attenuated. It is concluded that (i) tolerance is associated with depression of glyceryl trinitrate metabolism by an endothelium-independent mechanism and (ii) the endothelium contributes to tolerance by a mechanism which is independent of metabolism and may be linked with endothelial NOS.