Eda Karabal Kumcu

Effects of vitamin E and sodium selenate on neurogenic and endothelial relaxation of corpus cavernosum in the diabetic mouse

We studied the effect of vitamin E and sodium selenate treatment on the neurogenic and endothelium-dependent relaxation of isolated corpus cavernosum obtained from streptozotocin-induced diabetic mice. Relaxant responses of corpus cavernosum precontracted by phenylephrine to electrical field stimulation and to acetylcholine were significantly decreased in diabetic mice. There was no significant difference between diabetic and non-diabetic groups for the relaxant response of corpus cavernosum to sodium nitroprusside and papaverine. Treatment with sodium selenate, but not vitamin E, partially prevented the impairment of the neurogenic relaxation, whereas both had a significant, partial restorative action on endothelial dysfunction in corpus cavernosum obtained from diabetic groups. Neither agent exhibited a significant action on the relaxant responses of corpus cavernosum obtained from non-diabetic mice. A decrease in the sensitivity of the neurogenic impairment to antioxidant action may develop more rapidly than that of endothelial dysfunction in streptozotocin-induced diabetic mice.

Effect of phosphodiesterase type 4 inhibitor rolipram on cyclophosphamide-induced cystitis in rats

Cyclophosphamide induces a severe haemorrhagic cystitis characterized by bladder overactivity. The study was conducted to examine effects of a phosphodiesterase 4 (PDE4) inhibitor rolipram on bladder overactivity in rats with cyclophosphamide treatment. 42 female Wistar rats were used. 30 rats received a single i.p. injection of cyclophosphamide, and after 72 h, bladder function was evaluated by (1) in vitro preparations of whole bladders and (2) cystometry with continuous saline infusion under urethane anesthesia. Cyclophosphamide-treatment dramatically potentiated the basal spontaneous contractions of isolated whole bladders compared to control rats. Atropine, guanethidine or suramin was ineffective on the spontaneous contractions whereas nifedipine completely abolished. Rolipram (5-80 microM) induced a significant concentration-dependent decrease on the amplitude, frequency (contractions/min) and area under the curve of spontaneous contractions. Carbachol elicited phasic contractions superimposed on a tonic contraction. Rolipram caused a relaxation on the tonic contraction whereas it could not affect the phasic contractions induced by carbachol. In anesthetized rats, during continuous infusion cystometry, intercontraction interval was significantly shorter in cyclophosphamide-injected rats than in control rats. Rolipram at 5-40 microM has no significant effect on the intercontraction interval and contraction pressure while it significantly decreased pressure threshold. At 80 microM, it significantly decreased the intercontraction interval and contraction pressure. In conclusion, PDE4 inhibitor rolipram caused a significant decrease on the amplitude, frequency and area under the curve of basal spontaneous contractions in cyclophosphamide-treated rats, at doses that have no effect on the carbachol-induced phasic contractions and cystometric parameters. PDE4 inhibitors may be considered as an attractive strategy for the treatment of cyclophosphamide-induced bladder overactivity.

Restorative effects of zinc and selenium on nitrergic relaxations impaired by cadmium in the mouse corpus cavernosum.

We investigated whether Cd2+ intake (in drinking water, 15 ppm) for 30 days can affect the nitrergic relaxations of the mouse corpus cavernosum (CC) and whether Zn2+ (25 mg kg(-1) via a stomach tube at 48-h intervals) or sodium selenate (8 microg kg(-1) day(-1) intraperitoneally) has a restorative action on the impairment in the response. Relaxant responses of the CC obtained from Cd2+-treated mice to electrical field stimulation (neurogenic) or acetylcholine (endothelium dependent) were significantly inhibited. A partial restoration was observed in the nitrergic relaxation of the CC obtained from Zn2+- or sodium selenate-co-treated animals. Neither agent exhibited any significant action on the responses of the tissue from control mice. There was no significant difference between Cd2+-treated and control mice in respect of the relaxation amplitude induced by sodium nitroprusside or papaverine. These results suggest that Cd2+ intake may impair the nitrergic relaxation of the mouse CC, and, co-treatment with Zn2+ or sodium selenate may partially improve the nitrergic mechanisms in the tissue.

Differential effect of L-cysteine in isolated whole-bladder preparations from neonatal and adult rats.

The present study was undertaken to compare the effects of the thiol reagents l-cysteine and (diazene dicarboxylic acid bis 5N,N-dimethylamide) diamide on contractile activity of neonatal and adult rat bladders. In vitro whole-bladder preparations from Wistar rats were used to study the modulation of spontaneous bladder contractions by thiol reagents. After blocking cholinergic and adrenergic transmission with atropine and guanethidine, l-cysteine facilitated spontaneous bladder contractions in neonatal rat bladders. The effect of l-cysteine was suppressed by diamide. Diamide alone did not change basal activity of the neonatal rat bladder. The facilitatory effects of l-cysteine were reduced by the L-type Ca2+ channel-blocking agent nifedipine and the calcium-activated K+ channel opener NS1619 [1,3-dihydro-1-[2-hydroxy-5-(trifluoromethyl)phenyl]-5-(trifluoromethyl)-2H-benzimidazol-2-one]. ATP or suramin, a purinergic receptor antagonist, significantly inhibited the effect of l-cysteine in neonatal bladders, whereas the nitric-oxide synthase inhibitor Nω-nitro-l-arginine was ineffective. l-cysteine did not elicit any detectable effects in the adult rat bladder; whereas diamide caused a large-amplitude sustained tonic contraction. The contraction induced by diamide in adult bladder did not occur when the preparation was pretreated with l-cysteine. Also, l-Cysteine administered during the diamide-evoked contraction completely inhibited the contraction to diamide. In conclusion, our results suggest that l-cysteine has markedly different effects in isolated whole-bladder preparations from neonatal and adult rats. Thus thiol-sensitive mechanisms may modulate contractility by regulation of Ca2+ and K+ channels and/or purinergic transmission in the neonatal bladder. The effects of l-cysteine and diamide were reversed in adult bladders, indicating that the regulation of bladder contractility by thiols is markedly altered during postnatal development.

Effect of silymarin on bladder overactivity in cyclophosphamide-induced cystitis rat model.

The purpose of this study was to investigate the effects of silymarin, a phytotherapeutic agent, on bladder overactivity in a cyclophosphamide (CYP)-induced cystitis rat model. Female Wistar Albino rats received a single intraperitoneal injection of CYP (150 mg/kg) or saline and after 72 h, bladder function was evaluated by in vitro preparations of whole bladders and cystometry with continuous saline infusion under urethane anesthesia. Silymarin or a vehicle was orally given for 7 days in rats. CYP was injected on the 5th day of silymarin or vehicle treatment and then the animals were killed on the 8th day. CYP-treatment dramatically potentiated the basal spontaneous contractions of isolated whole bladders compared to control rats. In anesthetized rats, during continuous infusion cystometry, intercontraction interval (ICI) was significantly shorter, but bladder voiding pressure was not significantly changed in CYP-injected rats compared to control rats. In the CYP-injected group, silymarin treatment significantly decreased the amplitude, frequency (contractions/min) and area under the curve of spontaneous contractions, but failed to change carbachol-induced contraction in isolated whole bladder. Also, silymarin treatment significantly increased the ICI in comparison to the vehicle treatment. In the saline-injected group, no significant changes in the bladder function were observed between the silymarin and vehicle-treated groups. Histopathological examination showed that CYP-induced bladder inflammation tended to be lower in the silymarin+CYP-treated group. In conclusion, the oral administration of silymarin suppressed CYP-induced bladder overactivity. Silymarin may be considered as an attractive treatment for CYP-induced bladder overactivity.

Differential effect of neocuproine, a copper(I) chelator, on contractile activity in isolated ovariectomized non-pregnant rat, pregnant rat and pregnant human uterus.

The study was conducted to examine effects of a selective copper(I) chelator, neocuproine on the spontaneous or oxytocin-induced contractions in isolated ovariectomized non-pregnant rat, pregnant rat and pregnant human uterus. Uterus activity was evaluated in tissues obtained from bilaterally ovariectomized non-pregnant rats on the 21st day of the operation (n = 24), pregnant rats on the 19-21st day of gestation (n = 24) and women undergoing caesarean section at 38-42 weeks of pregnancy (n = 15). Neocuproine (100 microM) significantly suppressed the amplitude and frequency of the spontaneous contractions in the ovariectomized non-pregnant rat uterus while this agent facilitated the frequency of the spontaneous or oxytocin-induced contractions in the pregnant rat and human uterus without altering the amplitude of these contractions. At high concentration of 200 microM, neocuproine could enhance the amplitude of the contractions in the pregnant uterus. These effects were blocked by a purinergic receptor antagonist, suramin (100 microM) and did not occur following the administration of neocuproine-copper(I) complex or copper(II) chelator cuprizone. alpha, beta-methylene ATP increased the amplitude and frequency of contractions in the pregnant uterus, but not affected the contractions in the ovariectomized non-pregnant rat uterus, and neocuproine potentiated this facilitation effect. However, the suppressive effect of neocuproine on the ovariectomized non-pregnant rat uterus increased in the presence of alpha,beta-methylene ATP. Beta-adrenoceptor blocker, propranolol or nitric oxide synthase inhibitor, L-nitroarginine did not affect the responses to neocuproine. These findings suggest that neocuproine can affect the uterus contractile activity by modulation purinergic excitatory responses and that copper(I)-sensitive mechanisms may play a role in this effect.

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.

Effects of melatonin on impaired neurogenic and endothelial relaxations by bacterial lipopolysaccharide in the mouse corpus cavernosum.

We investigated whether bacterial lipopolysaccharide treatment causes any neuronal and vascular hyporeactivity in mouse cavernous tissue and also whether melatonin has any restorative effect on this possible neuronal and vascular hyporesponsiveness. Lipopolysaccharide treatment attenuated contractions in response to phenylephrine. Treatment with the inducible nitric oxide synthase inhibitor aminoguanidine or melatonin restored the hypocontractility of the cavernous smooth muscle to phenylephrine. Relaxant responses of corpus cavernosum precontracted by phenylephrine to acetylcholine or electrical field stimulation were significantly impaired in mice treated with bacterial lipopolysaccharide. Treatment with aminoguanidine or melatonin could prevent the impairment of the neuronal and endothelial relaxations. There was no significant difference between control and lipopolysaccharide-treated groups in the contractile response to high-dose KCl and in the relaxant response to papaverine. In conclusion, bacterial lipopolysaccharide treatment caused a neuronal and endothelial dysfunction in the mouse corpus cavernosum. A possible increased oxidative activity in the cavernous tissue may be a major reason for the impairment of relaxant responses and hypocontracility of tissue. The restorative effects of melatonin on this hyporeactivity may depend on its antioxidant properties and partly on its inhibitory action on the inducible nitric oxide synthase production.

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.

Evaluating the Teratogenicity of Ritodrine and Nifedipine using a Frog Embryo Teratogenesis assay (FETAX).

Abstract The Frog Embryo Teratogenesis Assay—Xenopus (FETAX) was used to assess the teratogenic potential of two tocolytics. Embryos of the South African clawed frog, Xenopus laevis, were exposed to ritodrine or nifedipine. Exposure media were changed and monitored at 24-hour intervals. The 96-hour LC50 (Lethal concentration), the 96-hour EC50 (Malformation), and the No Observable Adverse Effect Concentrations (NOAEC) and the Lowest Observable Adverse Effect Concentration (LOAEC) for mortality, malformation and length were determined for each drug. Nifedipine was determined to be the more toxic and teratogenic than ritodrine, with a LC50 of 0.606 µg/L, an EC50 of 0.006 µg/L, and a teratogenicity Index (TI) value (LC50/EC50) of 101. On the other hand, the LC50 of ritodrine was 28.571 mg/L. In addition; the LC50, EC50 and TI values for nifedipine in the 5 mg/L ritodrine + nifedipine combination group were determined as 1.050 µg/L, 0.868 µg/L and 1.5 respectively. For ritodrine, the NOAEC and LOAEC values were determined as 2 mg/L and 4 mg/L, respectively. For the nifedipine and the ritodrine + nifedipine groups; while the LOAEC values of these groups were 0.0001 µg/L and 0.1 µg/L, respectively. NOAEC value couldn’t be determined. Our results demonstrated that nifedipine administration was associated with higher levels of teratogenic and toxic effects. However, the ritodrine + nifedipine combination form reduced the toxic and teratogenic effects of nifedipine on Xenopus embryos. Further studies should be conducted in order to investigate the optimal combination concentrations of these substances for the treatment of preterm labor.