Investigation of enhancement effects of nicotine on cholinergic neurotransmission in isolated rabbit gastric fundus: role of antioxidants.

Nicotine, which is tobacco alkaloid, still induces interests for researchers because of smokers addiction to nicotine. Nicotine having influence on the neuronal acetylcholine receptors (nAChRs) increases release of most certain neurotransmitters from the nerve endings. Also, nicotine, affecting the mitochondrial respiratory chains, contributes to the formation of reactive oxygen species. In the present study, we investigated the effects of nicotine on smooth muscles of gastric fundus on the electrical field stimulation (EFS) that induces transition contraction via stimulation nAChRs. In addition, we aimed to investigate the interaction between release of acetylcholine, induced by nicotine, and the effects of reactive oxygen species. Therefore, the effects of allopurinol (10(-6)-10(-5) M), deferoxamine (10(-4) M) and mannitol (10(-4)-5 x 10(-3) M) were tested on the transient contraction induced by nicotine. In conclusion, mannitol (5 x 10(-3) M) significantly reduced contractile response to nicotine on EFS only in high concentration. Whereas in small concentrations mannitol (10(-4) M) statistically did not cause any results. Deferoxamine and allopurinol also did not have any significant response.

Effects of varicocele on electrical field stimulation-induced biphasic twitch responses in the ipsilateral and contralateral rat vasa deferentia.

AIM: Although little is known about the mechanisms, varicocele is considered as one of the factors leading to male infertility. Since reduced motility of the vas deferens was shown to contribute to male infertility, in this study we aimed to investigate the effect of varicocele on electrical field stimulation (EFS)-induced biphasic contractions of the vas deferens in order to evaluate the effect of varicocele on the motility of the vas deferens. MATERIAL AND METHODS: A total of 26 Sprague-Dawley rats (200-250 g) were assigned randomly into two groups: sham (n = 10) and varicocele (n = 16). Varicocele was produced by partial obstruction of the left renal vein. Four weeks after the surgical procedure, vasa deferentia were harvested and EFS-induced responses were recorded from the strips prepared from ipsilateral and contralateral sides via Grass isometric force displacement transducers. Exogenous alpha-beta methyl ATP was applied at the concentration of 10(-5)M to the vasa deferentia strips, and exogenous noradrenalin was applied cumulatively at the concentrations between 10(-7) and 10(-4)M. At the end of each experiment, 80 mM KCl was applied to induce contractions. All contractions were expressed as the percentage of the 80 mM KCl-induced contractions. RESULTS: Varicocele significantly inhibited both phases of EFS-induced biphasic contractions in the ipsilateral side, whereas in the contralateral site it did not produce any change. However, there was no change in exogenously applied alpha-beta methyl ATP, noradrenalin and KCl-evoked contractions of the vasa deferentia obtained from both sides. CONCLUSIONS: These results suggest that varicocele affects the ipsilateral vas deferens motility by reducing neurotransmitter release.

The effect of tryptophan administration on ileum contractility and oxidant status in mice.

L-tryptophan (TRP) is the precursor amino acid for the synthesis of serotonin (5-HT). 5-HT is effective both on the food intake and gastrointestinal system contractility. The aim of this study was to search the effects of systemic TRP treatment on 5-HT levels of ileum and searching the effect of ileal contractility and oxidant status. Swiss-albino mice were divided into two groups: 1. Control, 2. TRP-treated (100 mg/kg/24 h, i.p., for 7 days). Body weights were recorded at the beginning and at the end of experiments. Acetylcholine-induced contractile responses in the isolated ileum were recorded on polygraph. Ileal tissue malondialdehyde and glutathione levels determined by spectrophotometric and ileal tissue 5-HT levels were measured by immunohistochemical methods. TRP treatment decreased body weight and increased ileal contractile response. In the TRP-treated group, ileum malondialdehyde levels increased and glutathione levels decreased. Immunohistochemical detection showed that ileal 5-HT levels were increased by TRP treatment. There is a relationship between increased oxidative stress and increased contractility in the ileal tissue of the TRP-treated animals. These effects may be related to increased ileal 5-HT synthesis.

Tryptophan administration increase contractility and change the ultrastructure of mice duodenum.

Serotonin (5-HT) is a metabolite of tryptophan (TRP). 5-HT has been shown to induce contractions in rat duodenum and ileum. We planned to investigate the in vivo effects of TRP administration on duodenal contractility and ultrastructure together. Two equal groups of adult male Swiss-albino mice were used in the experiments. Controls (CONT) and TRP treated (100 mg/kg/24 hr in 0.2 ml. saline solution ip, 7 days). Body weights were recorded at the beginning and at the end of experiments. Duodenum tissues contractility responses to different concentration of KCl and acethycholine (ACh) were recorded on polygraph. The ultrastructural changes in duodenum observed by transmission electron microscopic (TEM) method and 5-HT levels determined by immunohistochemical method. Body weights decreased and duodenal contractile response of ACh increased significantly by TRP treatment. The duodenal ultrastructural changes in TRP group illustrated partially loss of apical surface and fusion in microvilli. Immunohistochemical detection showed that 5-HT increased by TRP treatment. There is a relation between duodenal contractility increased by TRP treatment and changes in the duodenal tissue 5-HT level and ultrastructure.

Nitric oxide and prostanoid-dependent relaxation induced by angiotensin II in the isolated precontracted mouse tracheal muscle and the role of potassium channels.

In this study we examined the mechanism of the concentration-dependent relaxant effect of angiotensin II (A II) on mouse isolated tracheal rings precontracted by carbachol. The contractile effect of carbachol is increased while the relaxant effect of A II decreased by pretreatment with N(G)-nitro-L-arginine methyl ester (L-NAME). This finding suggests that the L-arginine nitric oxide (NO) pathway is activated by the peptide. The relaxing effect of A II was also mediated through the release of cyclo-oxygenase products of arachidonic acid, as evidenced by the inhibition of the response by lysine acetylsalicylic acid (ASA) pretreatment. A II also caused a relaxation in the isolated tracheal rings precontracted by K(+)(>60 m m). K(+)-channel blockers partially inhibited the relaxant effect of A II in carbachol-precontracted mouse tracheal rings. A non-selective blocker of K(+)channels, tetraethylammonium, completely abolished the relaxation induced by A II. Among the other channel blockers, the inhibitory effect of apamine and glibenclamide was higher than that of iberiotoxin, indicating the involvement of K(ATP)and small conductance K(Ca)channels in the relaxing response to the octapeptide. These results suggest that the mechanisms, involved in the relaxation induced by A II in the isolated mouse tracheal rings precontracted by carbachol, were firstly l -arginine NO and cyclo-oxygenase products of arachidonic acid, secondly K(+)channels.

The contribution of nitric oxide and endothelins to angiotensin: II. Evoked responses in the rat isolated uterus smooth muscle.

The present study was designed to determine the role of endogenous endothelin peptides and nitric oxide on angiotensin II (All) responses in the isolated nonpregnant rat uterine smooth muscle. AII (10, 20, or 50 ng/ml) increases rhythmic oscillations dose dependently (32.7 +/- 8.9, 55.96 +/- 10.3, and 62.78 +/- 17.7% increase, respectively). L-arginine methyl ester (L-NAME; 10(-5) M) did not affect the increase in rhythmic oscillations induced by All (10, 20, or 50 ng/ml) (17.5 +/- 12.1, 31.5 +/- 18.3, and 52.5 +/-11.8% increase, respectively, n = 6, p > 0.05). It reduced the contractile responses to AII (10 ng/ml: from 4.63 +/- 0.6 to 1.8 +/-0.7 cm2, p < 0.05: and 20 ng/ml: from 5.59 +/- 0.8 to 2.11 +/- 0.4 cm2, p < 0.05, n = 6). L-arginine (10 mM) decreased the contractile response obtained by AII (10 or 20 ng/ml) (1.93 +/- 1.05, p < 0.05 and 2.14 +/- 0.7 cm2, p < 0.05, respectively, n = 6). BQ 485 (50 ng/ml) decreased both the number of rhythmic oscillations and the contractility increased by AII. Bosentan (10(-5) M) induced an increase in the number of rhythmic oscillations but decreased the contractile responses to the higher concentrations of All. These data show that endogenous NO and endothelin peptides contribute to the motility changes induced by AII and may play an important role in the pathophysiological events of the uterine function.

Does thromboxane A2 synthase inhibitor UK-38485 prevent the vasoconstrictor effects of endothelin-1 on rabbit basilar artery?

Prevention of the production of thromboxane A2--a potent vasoconstrictor and aggregating metabolite of arachidonic acid--or infusion of the stable analogues of prostacyclin--which is another cyclo-oxygenase metabolite of arachidonic acid--has been shown to be beneficial in cerebral vasoconstriction. Endothelin-1, a peptide derived from endothelial cells, has been shown to induce a long-lasting cerebral vasoconstriction both in vivo and in vitro. The purpose of this study was to investigate the role of a novel thromboxane A2-synthase inhibitor UK 38485 on the acute vascular and morphological effects of Endothelin-1 applied intra-arterially on rabbit basilar arteries. The inguinal region of twenty four anaesthetized albino rabbits of both sexes were dissected and a catheter was inserted into the aorta via the femoral artery, for control angiography of the basilar artery and intra-arterial injection of ET-1 (0.25 ng total dose) and UK 38485 at a dose of 0.05 microgram kg-1 min-1 for 20 min or saline. Angiographic vasoconstriction quantification and morphological investigations of both vessels and brain stem either by light microscopy or transmission electron microscopy were the techniques applied for the study. We found out that, although the systemic administration of UK 38485 resulted in a potent antagonism of the acute vasoconstriction as visualized in angiographic studies, it did not affect the morphological changes induced by Endothelin-1 on the vessel wall. The results indicated that there might have been an interaction between Endothelin-1 and the prostaglandin synthesis mechanism in acute cerebral vasoconstriction.

Nitric oxide-mediated relaxation induced by bradykinin in the isolated mouse trachea.

We examined the nature of the relaxant effect of bradykinin on mouse isolated tracheal rings. Bradykinin produced a concentration-dependent relaxation in mouse tracheal rings contracted by carbachol. Potentiation of the contractile effect of carbachol and inhibition of the relaxant effect of bradykinin by pretreatment with NG-nitro-L-arginine methyl ester (L-NAME), L-glutamine (L-Gln) and methylene blue (MeB) suggested that the peptide activated the L-arginine nitric oxide (NO) pathway. Part of the relaxant effect of bradykinin was also mediated through the release of cyclooxygenase metabolites of arachidonic acid, as evidenced by the inhibition of this response by lysine acetylsalicylic acid (ASA) pretreatment. Bradykinin also caused a relaxant response in precontracted tracheal rings in the presence of lower but not higher concentrations of K+ (> 60 mM). NG-nitro-L-arginine methyl ester and L-Gln did not alter the contractile effect of K+. K+ channel blockers partially inhibited the relaxant effect of bradykinin in carbachol-induced precontracted tracheal rings. Tetraethylammonium, a non-selective blocker of K+ channels, completely abolished the relaxant response to the peptide. Among the other channel blockers, the inhibitory effect of glibenclamide was slightly greater than that of apamine and iberiotoxin, indicating the involvement of K(ATP) channels in the relaxant response to the peptide. These results suggest that the mechanisms of the relaxation induced by bradykinin in carbachol-induced precontracted mouse tracheal muscle primarily involve activation of L-arginine NO and arachidonic acid cyclooxygenase pathways and secondly K+ channels.

In vitro susceptibility rhythms. II. Biological-time-dependent differences in effect of beta 1- and beta 2-adrenergic agonists of rat aorta and influence of endothelium.

Time-dependent variations in the vasodilator effects of beta-adrenergic agonists terbutaline (Ter) and dobutamine (Dob) were studied in isolated rings of rat thoracic aorta in both endothelium-intact and endothelium-denuded preparations. Rats were housed in light from 08:00 to 20:00 and in darkness from 20:00 to 08:00 and sacrificed at six different times of the day. In endothelium-intact and endothelium-denuded aortic rings precontracted submaximally with phenylephrine (Phe), addition of Ter and Dob produced concentration-dependent relaxations. Removal of endothelium reduced the relaxant responses and area under curve (AUC) values and augmented the EC50 values to Ter and Dob at most, but not all, time points. Two-way analysis of variance (ANOVA) revealed that AUCs, maximum responses, and EC50 values significantly depended on both treatment (endothelium intact/endothelium denuded) and time of sacrifice. Results of the present study clearly show that in vitro sensitivity of rat thoracic aorta to beta-adrenergic agonists displays temporal variations depending on the time of animal sacrifice, and the presence of endothelium modifies the rhythmicity in beta-adrenergic activity. These variations may be due to the circadian rhythmicity in the adenylyl cyclase-cAMP-phosphodiesterase system that mediates the responses to beta-adrenergic agonists.

The effects of captopril and naloxone on restraint-cold-stress- and ethanol-induced gastric lesions in rats.

1. This study was undertaken to investigate the effect of captopril (1 microgram/kg or 1 mg/kg, i.p.) on the actions of naloxone (5 mg/kg, i.p. in gastric ulceration induced by ethanol and restraint-cold-stress. 2. Neither naloxone (5 mg/kg, i.p.) nor captopril (1 mg/kg, i.p.) alone induced any change in the indices of the ulcer in either group. 3. Captopril at a lower dose (1 microgram/kg, i.p.), when combined with naloxone (5 mg/kg, i.p.), significantly reduced cumulative ulcer length only in the ethanol-treated group (from 54.9 +/- 7.2 mm to 22.5 +/- 6.2 mm). 4. However, a high dose of captopril (1 mg/kg) plus naloxone pretreatment caused a significant reduction in both ethanol (from 54.9 +/- 7.2 mm to 24.9 +/- 6.5 mm) and restraint-cold-stress (from 19.0 +/- 3.0 mm to 5.3 +/- 1.0 mm)-induced ulcer formation. 5. Acetylsalycilic acid, when used together with captopril, increased the ulcer formation induced by stress. 6. Naloxone, by increasing the release of prostaglandins, has been shown to prevent ulcer formation induced by several noxious stimuli. 7. Therefore, the effect of the combination might be due to the synergistic interaction of both drugs on prostaglandin synthesis.

In vitro evidence of tissue susceptibility rhythms. I. Temporal variation in effect of potassium chloride and phenylephrine on rat aorta.

In this study, time-dependent variations in the in vitro sensitivity of rat thoracic aorta rings to potassium chloride (KCl) and phenylephrine (Phe) were investigated. Animals were synchronized with a 12h light and 12h darkness (lights on 08:00-20:00) schedule, and thoracic aortas were obtained at six different times of the day (1, 5, 9, 13, 17, and 21 hours after lights on). In order to avoid endothelial influence, all experiments were performed in endothelium-denuded preparations. Responses to KCI showed time-dependent variations in all the concentrations used. Phe-induced contractions also exhibited time-dependent differences. The rhythmic pattern of Phe responses did not change with the presence of the alpha1-adrenergic antagonist prazosin. In addition, both the EC50 values of KCl and Phe, and also the K(B) values of prazosin, displayed rhythmicity. In conclusion, time of obtaining tissues is an important factor for experimental standardization in, at least, vascular smooth muscle preparations.

Changes of arterial arachidonic acid metabolites in hypertensive patients during haemodialysis.

It is well known that in haemodialysis patients suffering from oligoanuria, extracellular hypervolaemia develops and this hypervolaemia is the main reason for hypertension occurring in some of the patients. The absence of vasorelaxation during hypervolaemia may be secondary to an increased activity of vasoconstrictor systems and/or a decreased formation of vasodilator agents like prostaglandin E2(PGE2) and prostaglandin I2(PGI2). In the present study, arterial PGE2 and leukotriene C4(LTC4)-like activities and the effect of fluid removal on these arachidonic acid metabolites during haemodialysis were measured in normotensive and hypertensive patients. Plasma PGE2 and LTC4-like activities were significantly different between hypertensive and normotensive patients. PGE2/LTC4 ratio did not change in normotensive patients while it was increased in hypertensive patients after haemodialysis. These results indicate that haemodialysis alters the synthesis of arachidonic acid metabolites especially in hypertensive patients.

Twenty-four-hour variations in the effect of nitrodilators in rat aorta: lack of influence of the endothelium.

Time-dependent variations of the vasodilator effects of sodium nitroprusside and glyceryl trinitrate on isolated smooth muscle have been studied on rings of rat thoracic aorta, both endothelium-intact and endothelium-denuded. For most of the concentrations of sodium nitroprusside used the induced relaxations were significantly dependent on the time the tissues were obtained. However, significant temporal differences were obtained for glyceryl trinitrate-induced relaxations at lower concentrations only for both endothelium-intact and endothelium-denuded preparations. EC50 values of sodium nitroprusside and glyceryl trinitrate (i.e. the concentrations inducing half the maximum response) were also significantly different and they had quite similar rhythmic features both in endothelium-intact and in endothelium-denuded preparations. These results clearly show that the in-vitro sensitivity of rat thoracic aorta to nitrodilator agents varies over a 24-h period and thus depends on when the animals were killed; the presence of endothelium does not change the rhythm of nitrodilator activity. These variations might be a result of circadian rhythm in the guanylate cyclase-cGMP system which mediates responses to nitrodilator agents.

The mechanism of the relaxing effect of ascorbic acid in guinea pig isolated tracheal muscle.

1. The effect of ascorbic acid was studied in the guinea pig isolated tracheal muscle. 2. Ascorbic acid with relatively higher concentrations produced a dose-dependent relaxation in tracheal muscle submaximally precontracted with KCl, histamine, and carbachol. 3. Removing the epithelium did not significantly alter the relaxing effect of ascorbic acid in histamine- and KCl-precontracted strips. 4. The relaxing effect of ascorbic acid is stronger in carbachol-precontracted epithelium-denuded strips than in epithelium-intact strips. 5. Indomethacin, but not L-NAME, partially inhibited the relaxing effect of ascorbic acid. 6. These results indicate that the relaxation induced by ascorbic acid in guinea pig isolated tracheal muscle does not fully depend on the presence of epithelium but is partially mediated by the production of prostanoids from smooth muscle.

Effect of nordihydroguaretic acid and fluconazole on the LTC4/PGE2 ratio in the kidney of mice damaged by Candida albicans.

The kidney is a major target organ in generalized candidiasis. When mice were infected with C.albicans, prostaglandin E2 (PGE2)-like activity was found to be significantly decreased while leukotriene C4 (LTC4)-like activity increased in the kidneys within 10 days. The aim of this study is to investigate the effect of nordihydroguaretic (NDGA) and fluconazole on the LTC4/PGE2 ratio in the mice kidneys infected by proteinase (+) C. albicans. The LTC4/PGE2 ratio was found to be significantly decreased both in NDGA and fluconazole-pretreated groups. These results indicate that pretreatment with the lipoxygenase inhibitor NDGA and the antifungal drug fluconazole, protect the kidney against C. albicans infection. These results also indicate a possible role of arachidonic acid metabolites (increase LTC4 and decrease PGE2) in kidney damage due to C. albicans infection.

The cytoprotective effect of iloprost against carbon tetrachloride induced necrosis in rat liver.

The aim of this study was to investigate the cytoprotective effect of Iloprost on the liver against carbon tetrachloride induced necrosis. The serum histamine-like activity was found to be increased when compared with that of controls after treatment with carbon tetrachloride for 18 weeks while prostaglandin E2- and leukotriene C4-like activities were unchanged. After pretreatment with Iloprost for 18 weeks the increased activity of histamine was found to be unchanged while prostaglandin E2-like activity was increased. It is concluded that Iloprost protects the liver against carbon tetrachloride-induced damage and reduces the level of histamine that has a role in the pathogenesis of portal hypertension.

Increased serum leukotriene B4 level in the active stage of rheumatoid arthritis in children.

The possible association of leukotriene B4 (LTB4)-like activity with the development of active rheumatoid arthritis was studied in 25 children with the disease and in 15 normal subjects. Serum LTB4-like activity was found to be significantly higher in the active stage of the disease when compared with the values obtained from patients during the inactive stage and from healthy children. No correlation was found between LTB4-activity and other laboratory parameters, e.g. haemoglobin level, white cell count and erythrocyte sedimentation rate.

Parathormone, 1,25 dihydroxyvitamin D and prostaglandin E2 correlation in children with idiopathic hypercalciuria.

As urinary prostaglandin excretion might be involved in idiopathic hypercalciuria, we studied the excretion of prostaglandin E2 and calcium together with serum prostaglandin E2, parathormone and 1,25 dihydroxyvitamin D in 20 patients and 11 controls Idiopathic hypercalciuric patients showed increased levels of urinary prostaglandin E2-like activity, which is correlated with calcium excretion. Although no change was observed in serum parathormone level in control and hypercalciuric patients, there was a positive correlation between serum 1,25 dihydroxyvitamin D and prostaglandin E2-like activity. These findings suggest that prostaglandin E2 could play a role in the hypercalciuria syndrome, possibly by increasing 1,25 dihydroxyvitamin D synthesis.

An unexpected interaction between NG-nitro-L-arginine methyl ester and L-arginine in alpha-naphthylthiourea-induced pulmonary oedema in rats.

This study was designed to investigate the possible participation of the L-arginine-nitric oxide (NO) pathway in the lung oedema induced by alpha-naphthylthiourea, which is a well-known noxious chemical agent in the lung. Lung oedema was assessed by measuring fluid accumulation in the pleural cavity and the lung weight/body weight ratio following alpha-naphthylthiourea injection. Administration of NG-nitro-L-arginine methyl ester, a NO synthase inhibitor, prior to alpha-naphthylthiourea, produced a significant inhibition of pleural effusion and lung weight/body weight ratio in a dose-dependent manner. L-Arginine, but not D-arginine, when used higher doses (above 300 mg/kg) prior to alpha-naphthylthiourea injection caused a significant inhibition of pleural effusion without altering lung weight/body weight ratio. Lower doses of L-arginine (below 100 mg/kg) did not elicit an inhibitory effect against alpha-naphthylthiourea-induced pulmonary damage. However, lower doses of L-arginine greatly potentiated the inhibitory effect of NG-nitro-L-arginine-methyl ester against alpha-naphthylthiourea-induced lung oedema when used in combination. The interesting aspect of this study is the inhibition by NG-nitro-L-arginine methyl ester, a NO synthase inhibitor, and L-arginine, an endogenous donor of NO, of the lung oedema induced by alpha-naphthylthiourea. The possible role of the L-arginine-NO pathway in lung oedema induced by alpha-naphthylthiourea and the possible underlying mechanisms are discussed.

Early phase alterations in endothelium dependent vasorelaxation responses due to aneurysm clip application and related manipulations.

Mechanically induced vasoconstriction observed throughout surgery and in the immediate postoperative period was investigated to assess the effects of various microsurgical manipulations. Factors such as the type of aneurysm clip, duration of temporary clipping and peri-adventitial tissue stripping were the variables in this study. Microsurgical clips were applied on guinea pig "cervical carotid arteries" in which peri-adventitia had been removed microsurgically. Arterial rings were removed immediately after surgery. Endothelium dependent relaxations were measured and morphological investigations were performed using light microscopy. It was observed that as the clip application period increased, relaxation responses decreased. Peri-adventitial tissue stripping caused a marked decrease in the relaxation responses in all types of the clips. Microvascular clips, in spite of their lower closing forces, had the greatest deleterious effect on relaxation responses of the vessel, in both normal and peri-adventitial tissue stripped. When the peri-adventitial tissue of the vessel had been stripped, convolutions of the lamina elastica interna were found to be lost in parallel with the decreased tonus of the artery. In the vessels subjected to clipping endothelial denudation and cracking took place. As a conclusion it can be stated that both peri-adventitial tissue stripping and microvascular clip application have deleterious effects in the early postoperative period. While choosing clips from minimal occlusion force tables, care must be taken to choose clips with less width; and while performing microvascular anastomosis, temporary clips with a lesser width must be used in place of microvascular clips. Adventitial stripping must not be unnecessarily generous during microvascular anastomosis.