Search results for " Methyl ester"
showing 10 items of 127 documents
Modulation by nitric oxide of spontaneous mechanical activity in rat proximal colon.
1999
Summary 1 In order to examine the role of nitric oxide (NO) in the tonic neural inhibition in rat proximal colon, the effects of Nω-nitro- l-arginine methyl ester (L-NAME) were studied on the spontaneous contractions of circular muscle (monitored as intraluminal pressure changes) and of longitudinal muscle (detected as isometric tension changes). 2 L-NAME (3 × 10−−6–3 × 10−−4 m) caused a concentration-dependent increase in the amplitude of circular contractions, without affecting those of longitudinal muscle. This effect was prevented by l-arginine (1–5 × 10−−3 m), but not d-arginine. 3 In the presence of tetrodotoxin (10−−6 m), which per se induced increase of the pressure waves, L-NAME (1…
Calcium dependence of the contraction produced by endothelin (ET-1) in isolated guinea-pig trachea.
1990
Endothelin (ET-1, 1 pM to 0.1 microM) produced a concentration-dependent contraction of isolated guinea-pig trachea. BAY K 8644 (1 microM) did not significantly alter the concentration-response curve for ET-1. Incubation with nicardipine (10 microM) partly inhibited responses to low concentrations (10 pM to 1 nM) of ET-1 while verapamil (10 microM) and diltiazem (10 microM) were ineffective. La3+ (10 microM) and Cd2+ (10 microM) preferentially depressed the responses evoked by high concentrations (30 nM-0.1 microM) of ET-1 without affecting the responses evoked by low concentrations of the peptide. Incubation in Ca2(+)-free (with EDTA, 1 mM) medium resulted in suppression of the responses e…
Modulation of adrenergic contraction of dog pulmonary arteries by nitric oxide and prostacyclin.
1999
Abstract The aim of this work was to investigate the influence of endothelium-derived nitric oxide and prostaglandins on the contractile responses of isolated dog pulmonary arteries to electrical field stimulation and noradrenaline. Electrical field stimulation (1–8 Hz, 20 v, 0.25 ms duration, for 30 s) produced frequency-dependent contractions that were abolished by tetrodotoxin, guanethidine and, prazosin (all at 10−6 M). Noradrenaline induced concentration-dependent contractions with an EC50 of 1.85 × 10−6 M. The increases in tension induced by electrical stimulation and noradrenaline were of greater magnitude in arteries denuded of endothelium. In segments with endothelium, NG-nitro- l …
Endogenous nitric oxide is responsible for the early loss of P450 in cultured rat hepatocytes
1998
AbstractLoss of P450 during the early hours of monolayer formation is known to be the more serious limitation of primary cultured hepatocytes as an adequate model for the study of drug metabolism, toxicity and P450 induction. This study reports that endogenous nitric oxide (NO) formation is activated shortly after isolation by the classical collagenase-based liver perfusion methods. Both rapid P450 loss and aerobic mitochondrial energy metabolism impairment – with subsequent changes on glucose metabolism – are directly related to the high local generation of the radical at this stage. These effects can be reverted by the sole addition of NO biosynthesis inhibitors during liver perfusion and…
Doxycycline reduces nitric oxide production in guinea pig inner ears.
2011
Abstract Objective Gentamicin application is an important therapeutic option to control vertigo spells in Meniere's disease. However, even in the case of low-dose intratympanic application, gentamicin might contribute to a pathological NO-increase leading to cochlear damage and hearing impairment. The study was performed to evaluate the nitric oxide (NO) reducing capacity of doxycycline in the inner ear after NO-induction by gentamicin. Methods In a prospective animal study, a single dose of gentamicin (10 mg/kg body weight) was injected intratympanically into male guinea pigs (n = 48). The auditory brainstem responses (ABRs) were recorded prior to application and 3, 5 and 7 days afterwards…
Chronic Therapy With Isosorbide-5-Mononitrate Causes Endothelial Dysfunction, Oxidative Stress and a Marked Increase in Vascular Endothelin-1 Express…
2011
Aims Isosorbide-5-mononitrate (ISMN) is one of the most frequently used compounds in the treatment of coronary artery disease predominantly in the USA. However, ISMN was reported to induce endothelial dysfunction, which was corrected by vitamin C pointing to a crucial role of reactive oxygen species (ROS) in causing this phenomenon. We sought to elucidate the mechanism how ISMN causes endothelial dysfunction and oxidative stress in vascular tissue. Methods and results Male Wistar rats ( n = 69 in total) were treated with ISMN (75 mg/kg/day) or placebo for 7 days. Endothelin (ET) expression was determined by immunohistochemistry in aortic sections. Isosorbide-5-mononitrate infusion caused si…
Inhibition of gastric acid secretion by stress: A protective reflex mediated by cerebral nitric oxide
1996
Moderate somatic stress inhibits gastric acid secretion. We have investigated the role of endogenously released NO in this phenomenon. Elevation of body temperature by 3°C or a reduction of 35 mmHg (1 mmHg = 133 Pa) in blood pressure for 10 min produced a rapid and long-lasting reduction of distension-stimulated acid secretion in the rat perfused stomach in vivo . A similar inhibitory effect on acid secretion was produced by the intracisternal (i.c.) administration of oxytocin, a peptide known to be released during stress. Intracisternal administration of the NO-synthase inhibitor, N G -nitro- l -arginine methyl ester ( l -NAME) reversed the antisecretory effect induced by all these stimul…
Relaxant effect of sildenafil in the rabbit basilar artery
2005
We hypothesized that sildenafil, inhibitor of phosphodiesterase-5 (PDE-5), interacts with the nitric oxide (NO)-cGMP pathway in the cerebral arteries and shows vasoactive effects. To prove it in the isolated rabbit basilar artery, we compared the effects of sildenafil with other PDE-5 inhibitors, assessed the endothelial dependence of the vasoactive responses, and used modulators of the cGMP and cAMP signaling processes. Sildenafil (10 nM-0.1 mM) induced concentration-dependent relaxations of endothelin-1 (10 nM)-precontracted basilar artery, which were partially inhibited both in endothelium-denuded arteries and in arteries precontracted by depolarization with KCl (50 mM). Endothelin-1 (1 …
Inhibition of mechanical activity by neurotensin in rat proximal colon: involvement of nitric oxide.
1997
The aim of the present study was to define the nature of inhibitory action of neurotensin in rat proximal colon. Mechanical activity was detected as changes of intraluminal pressure. Neurotensin (10(-10) to 10(-7) M), in the presence of atropine (10(-6) M), guanethidine (10(-6) M), and nifedipine (10(-8) M), induced a tetrodotoxin-insensitive inhibitory effect characterized by the complete disappearance of the spontaneous phasic contractions. The inhibitory effect of neurotensin (10(-7) M) was abolished by scorpion venom (Leiurus quinquestriatus hebraeus) (10(-6) g/ml) or high K+ (40 mM KCl), whereas it persisted in the presence of omega-conotoxin GVIA, (10(-7) M). N omega-nitro-L-arginine…
Glucagon-like peptide-2 relaxes mouse stomach through vasoactive intestinal peptide release.
2009
Glucagon-like peptide-2 (GLP-2) influences different aspects of the gastrointestinal function, including epithelial growth, digestion, absorption, motility, and blood flow. Intraluminal pressure from isolated mouse stomach was recorded to investigate whether GLP-2 affects gastric tone and to analyze its mechanism of action. Regional differences between diverse parts of the stomach were also examined using circular muscular strips from fundus and antrum. In the whole stomach, GLP-2 (0.3–100 nM) produced concentration-dependent relaxation with a maximum that was about 75% of relaxation to 1 μM isoproterenol (IC50 = 2.5 nM). This effect was virtually abolished by desensitization of GLP-2 rece…