Non-selective NO-synthase Inhibitor L-NAME Research Articles

The Role of NO Synthase in the Infarct-Limiting Effect of Urgent and Chronic Adaptation to Normobaric Hypoxia.

We studied the role of NO synthase in the infarct-limiting effect of short-term (SNH) and chronic continuous normobaric hypoxia (CNH). In male Wistar rats, SNH (6 sessions of 10-min hypoxia 8% O2 and 10-min reoxygenation) or CNH (12% O2 for 21 days) was modeled. In 30 min after SNH or 24 h after CNH, the rats were subjected to coronary artery occlusion (45 min) and reperfusion (2 h). The following drugs were administered to rats: non-selective NO synthase inhibitor L-NAME (10 mg/kg), inhibitor of inducible NO synthase S-methylthiourea (3 mg/kg), and inhibitor of neuronal NO-synthase 7-nitroindazole (50 mg/kg). NO donor diethylenetriamine was administered intravenously in a dose 2 mg/kg. It was found that L-NAME and S-methylthiourea abolished the infarct-limiting effect of SNH and CNH. Diethylenetriamine increased cardiac tolerance to ischemia/reperfusion. It is believed that inducible NO synthase plays an important role in the cardioprotective effect of normobaric hypoxia.

ENDOTHELIOPROTECTIVE AND ANTIAGGREGANT EFFECT OF PRIMULA VERIS L. SOLID HERBAL EXTRACT IN EXPERIMENTAL CHRONIC HEART FAILURE

Were studied endothelioprotective and antiaggregant properties of Primula veris L. solid herbal extract (PVSHE) in animals under experimental chronic heart failure (CHF) caused by isoproterenol administration in a dose of 2,5 mg / kg twice a day for 21 days. It was shown that in the control group of animals with CHF, the introduction of acetylcholine increased by 21,2 %, while the non-selective NO-synthase inhibitor L-NAME reduced the rate of blood flow in the carotid artery of rats by 27,5 %, which was less than the same values in the intact group: 45,2 % and -46,8 %, respectively (p < 0,05). The introduction of acetylcholine caused an increase in the rate of blood flow in the carotid artery in rats with CHF who received PVSHE at a dose of 30 mg / kg by 43,4 % and mildronate at a dose of 50 mg / kg - by 43,8 %, which was significantly higher than in animals of the control group (p < 0,05). The non-selective inhibitor of NO-synthase L-NAME reduced blood flow in the animals with CHF receiving study medications: -40,4 % and -39,5 % (p < 0,05), respectively It was found that the rate and degree of aggregation of platelets was higher in rats with CHF than in intact animals (29,6 % / min versus 20,6 % / min and 27,3 % vs. 18,8 %, p < 0,05, respectively ). In rats with CHF receiving PVSHE, the rate of blood flow in the carotid artery was 20% / min, mildronate -23,2 % / min, the degree of aggregation was 19 % and 21,9 %, respectively which was significantly lower in comparison with animals of the control group (p < 0,05). It was found that the level of von Willebrand factor (vW) was higher in animals with CHF than in the intact group by 91,1 % (p < 0.05) and significantly lower in animals with CHF who received PVSHE by 31,4 % (p < 0,05) and mildronate 21,2 % relative to the control group of rats (p < 0,05). The obtained data testify to the endothelioprotective and antiaggregant effect of the PVSHE comparable to the comparative preparation mildronate.

Metabolic changes in pulmonary mitochondria of rats with experimental hyperhomocysteinemia

Hyperhomocysteinemia is a risk factor for many human diseases, including pulmonary pathologies. In this context much interest attracts secondary mitochondrial dysfunction, which is an important link in pathogenesis of diseases associated with hyperhomocysteinemia. The study was conducted using male Wistar rats. It was found that under conditions of severe hyperhomocysteinemia caused by administration of methionine, homocysteine was accumulated in lung mitochondria thus suggesting a direct toxic effect on these organelles. However, we have not observed any significant changes in the activity of mitochondrial enzymes involved in tissue respiration (succinate dehydrogenase) and oxidative phosphorylation (H+-ATPase) and of cytoplasmic lactate dehydrogenase. Also there was no accumulation of lactic acid in the cytoplasm. Animals with severe hyperhomocysteinemia had higher levels of lung mitochondrial protein carbonylation, decreased reserve-adaptive capacity, and increased superoxide dismutase activity. These results indicate that severe hyperhomocysteinemia causes development of oxidative stress in lung mitochondria, which is compensated by activation of antioxidant protection. These changes were accompanied by a decrease in the concentration of mitochondrial nitric oxide metabolites. Introduction to animals a nonselective NO-synthase inhibitor L-NAME caused similar enhancement of mitochondrial protein carbonylation. It demonstrates importance of reducing bioavailability of nitric oxide, which is an antioxidant in physiological concentrations, in the development of oxidative stress in lung mitochondria during hyperhomocysteinemia. Key words: hyperhomocysteinemia, nitric oxide, lung, oxidative stress, mitochondria.

Spatial Memory in the Progeny of Rats Subjected to Different Types of Experimental Preeclampsia.

Spatial memory was studied in 2-month-old offspring of rats subjected to different types of experimental preeclampsia (replacement of drinking water with 1.8% NaCl from day 1 to 21 of gestation or intraperitoneal administration of non-selective NO-synthase inhibitor L-NAME to pregnant rats in a daily dose of 25 mg/kg for 7 days on gestation days 14-20). Spatial memory was evaluated in an elevated 8-arm radial maze. Both types of experimental preeclampsia impaired spatial (long-term and short-term) memory and can be used in the development of drugs correcting negative effects of this pregnancy complication on memory.

Effect of NO synthase blockade on NO production in rat heart under conditions of hypokinesia.

Electron paramagnetic (EPR) spectroscopy study showed that 90-day hypokinesia in rats is accompanied by an increase in NO production in the heart. A nonselective NO synthase inhibitor L-NAME decreased the content of NO in the heart atria and ventricles of hypokinetic rats by 67-70%. A selective inhibitor of inducible NO synthase, aminoguanidine, also decreased the level of NO in the heart atria and ventricles of hypokinetic rats by 60-65%. Our results indicate that the increase in NO production during hypokinesia is associated with activation of NO synthases.

Effects of Selective Inhibitors of Neuronal and Inducible NO-Synthase on ATP Content and Survival of Cultured Rat Cerebellar Neurons during Hyperstimulation of Glutamate Receptors

We studied the effects of selective inhibitors of neuronal and inducible NO-synthase (7-nitroindazole and aminoguanidine) and non-selective NO-synthase inhibitor L-NAME on ATP content and survival of cultured rat cerebellar neurons during hyperstimulation of glutamate receptors with toxic doses of glutamate. Application of 100 μM glutamate reduced ATP content in the primary culture of 7-8- and 14-15-day-old cerebellar granule cells by 66 and 49%, respectively, in comparison with the control. Inhibition of nitric oxide synthesis with 7-nitroindazole during glutamate exposure in the culture of 7-8-day-old neurons and with 7-nitroindazole and aminoguanidine in the culture of 14-15-day-old neurons ensured better protection of cells from ATP level decrease than non-specific inhibition with L-NAME. In addition, inhibition of neuronal and inducible NO-synthase during glutamate exposure decreased death of "young" neurons, whereas death of "old" neurons remained high under these conditions.

Вплив каліксарену С-90 на скоротливу активність гладеньких м’язів міометрія щурів

It is known that calix[4]arene with cipher C-90 selectively and with high affinity inhibits Ca 2+ ,Mg 2+ -ATPase of smooth muscle cells plasma membrane preparations. The work wis devoted to investigation of the influence of calixarene C-90 (10 µM) on spontaneous and induced (high-potassium solution and oxytocin) contractions of rat uterus longitudinal smooth muscles. Contractile activity was studied tensometrically in the isometric mode, analysis of the kinetic properties of contractions was performed by the calculation of the normalized maximal velocity of contraction ( V n с ) and relaxation ( V nr ) phases. Calixarene C-90 changed the spontaneous contractile activity, causing a decrease in amplitude and has no significant effect on the frequency, while slowing down of the relaxation phase of individual contractions (decreasing parameter V nr ) occurred. In the presence of non-selective NO-synthase inhibitor L-NAME (100 µM), calixarene C-90 did not cause a reduction of the amplitude of spontaneous contractions and the speed of relaxation phase returned to the control level. Furthermore, calixarene C-90 was equally contributing factor to reduced force of both oxytocin-induced (0.1 IU) and K + -induced (80 mM) contractions without affecting the nature of the increase in contractile force responses (normalized maximal velocity of contraction phase stayed at control level). The relaxation velocity of caused contractions recieved opposite changes depending on the nature of the contractile stimulation: in case of oxytocin-evoked contractions – decreased, while for K + -induced contractions – increased. In the presence of L-NAME calixarene C-90 did not cause inhibition of the maximal force K + - and oxytocin-induced contractions, but evoked changes in the kinetical para­meters of contractile responses (decrease V nr ). Thus, blocking of NO synthesis resulted in the removal of inhibiting both spontaneous and evoked contractions of smooth muscle myometrium under the influence of calixarene C-90. These results suggest that inhibition force of uterus smooth muscle contractions under the influence of calixarene C-90 is by NO-dependent way, whereas slow relaxation (decrease in normalized maximal velocity V nr ) is caused by the inhibition of Ca 2+ -transport function of the plasma membrane calcium pump. Keywords : smooth muscle, uterus, contraction, kinetical parameters, calixarene C-90, plasma membrane calcium pump, nitric oxide.

Effect of a Blocker of Nitric Oxide Production on Albumin Excretion by Rat Kidney

Experiments on Wistar rats showed that single intraperitoneal injection nonselective NO-synthase inhibitor L-NAME in a dose of 50 mg/kg was followed by transient proteinuria and albuminuria. This effect was not reproduced by injection of ODQ, an inhibitor of intracellular effects of NO, and arginine, but D-NAME, an optical isomer of L-NAME not blocking NO-synthase, produced similar, though less pronounced effect. The degree of proteinuria and albuminuria increased in combined treatment with nitroarginine methyl esters and 1-deamino-arginine vasotocin or arginine vasopressin. Proteinuria during treatment with arginine derivatives attests to not only their effect on the charge of the filtration membrane, but also the participation of NO-dependent processes in the regulation of ultrafiltration in renal glomeruli.

7-NITROINDAZOLE, BUT NOT L-NAME OR AMINOGUANIDINE, ATTENUATES ANAPHYLACTIC HYPOTENSION IN CONSCIOUS RATS

The roles of NO and isozymes of NO synthase (NOS) are not known in anaphylactic hypotension of unanesthetized rats. Effects of inhibition of NOS, iNOS, and nNOS by N-nitro-L-arginine methyl ester (L-NAME), aminoguanidine, and 7-nitroindazole, respectively, were determined on the antigen-induced systemic hypotension and portal hypertension in conscious Sprague-Dawley rats sensitized with the ovalbumin antigen. The MAP and portal venous pressure were directly and simultaneously measured. The control rats showed a decrease in MAP along with an increase in portal venous pressure but did not die within 48 h after antigen injection. In the rats pretreated with the nonselective NOS inhibitor L-NAME (10 mg/kg), MAP before and after antigen administration was significantly higher than that of the control rats, but the net decrease in MAP and increase in portal venous pressure were rather greater than those of the control, resulting in fatal outcome within 12 h after antigen administration. In contrast, pretreatment with the relatively selective nNOS inhibitor 7-nitroindazole (50 mg/kg) substantially attenuated anaphylactic hypotension over 20 min after antigen administration, whereas the relatively selective iNOS inhibitor aminoguanidine (100 mg/kg) did not affect it. In conclusion, in anaphylactic hypotension of unanesthetized rats, NO derived from nNOS, but not from iNOS, may be involved, and the nonselective NOS inhibitor L-NAME is lethal.

Parasympathetic nerve-evoked protein synthesis, mitotic activity and salivary secretion in the rat parotid gland and the dependence on NO-generation

Incorporation of radiolabelled leucine and thymidine into trichloroacetic acid-insoluble material of the parotid gland was used as indices of protein synthesis and mitotic activity, respectively, following electrical stimulation of the parasympathetic auriculo-temporal nerve for 30 min in pentobarbitone-anaesthetized rats under adrenoceptor blockade (phentolamine and propranolol, 2mg/kg intravenous of each) in the absence or presence of atropine (2mg/kg intravenous) and without or with nitric oxide synthase inhibitors. In atropinized rats, the parasympathetic non-adrenergic, non-cholinergic (NANC) nerve-evoked mean increases in protein synthesis at a frequency of 10 Hz (142%) and 40 Hz (200%) were not affected in a statistically significant way (124 and 275%, respectively) by the neuronal type NO-synthase inhibitor N(w)propyl-l-arginine (N-PLA) (30 mg/kg intravenous). Neither were the increase (175%) in protein synthesis at 10 Hz in non-atropinized animals affected by N-PLA (180%). The increase (65%) in mitotic activity, 19 h after the end of stimulation at 40 Hz, in the presence of atropine, was not affected by N-PLA (55%). Neither were the increase (95%) in gland content of amylase at this point of observation statistically significant affected by N-PLA (144%). The secretion of fluid and output of amylase from the parotid gland upon nerve stimulation was not affected by N-PLA. When examining the non-selective NO-synthase inhibitor l-NAME (30 mg/kg intravenous) in atropinized rats subjected to stimulation at 10 Hz, neither the increase in protein synthesis nor the evoked fluid response or amylase outputs were affected. Hence, in contrast to an NO-dependent sympathetic-induced protein synthesis and mitosis in the parotid gland, involving the activity of the neuronal type NO-synthase, no support for a parasympathetic-induced protein synthesis (and gain in gland amylase) and mitosis, depending on NO-generation, was found. Likewise, the present findings provide no evidence for a role of NO in the parasym pathetic nerve-evoked fluid secretion and amylase output.

Nitric oxide-dependent protein synthesis in parotid and submandibular glands of anaesthetized rats upon sympathetic stimulation or isoprenaline administration.

In anaesthetized female rats, the beta-adrenoceptor agonist isoprenaline was intravenously infused (20 microg kg(-1) min(-1)) for 30 min or the ascending cervical sympathetic nerve trunk was intermittently stimulated (50 Hz, 1 s every tenth second) on one side for 30 min. The incorporation of [3H]leucine into trichloroacetic acid (TCA)-insoluble material was used as an index of protein synthesis. In response to isoprenaline, the [3H]leucine incorporation increased by 79% in the parotid glands and by 82% in the submandibular glands. The neuronal type NO-synthase inhibitor N-PLA, reduced (P < 0.001) this response to 26% and 20%, respectively. Sympathetic stimulation under alpha-adrenoceptor blockade increased the [3H]leucine incorporation by 192% in the parotid glands and by 35% in the submandibular glands. N-PLA reduced the corresponding percentage figures to 86% (P < 0.01) and 8% (P < 0.05). When tested in the parotid glands, the non-selective NO-synthase inhibitor L-NAME reduced (P < 0.01) the nerve-evoked response to 91%. The increase in [3H]leucine incorporation in response to sympathetic stimulation under beta-adrenoceptor blockade was not affected by N-PLA in the parotid (139% versus 144%) and submandibular glands (39% versus 34%). In non-stimulated glands, the [3H]leucine incorporation was not influenced by the NO-synthase inhibitors. In conclusion, beta-adrenoceptor mediated salivary gland protein synthesis is largely dependent on NO generation by neuronal type NO-synthase, most likely of parenchymal origin.

The changes of the thyroid function and serum testosterone levels after long-term L-NAME treatment in male rats.

Nitric oxide is a highly reactive gas that is produced by many tissues and exerts a series of physiological and pathophysiological effects. We studied the changes of the serum testosterone, thyroxine and thyrotropin levels, thyroid and anterior pituitary weights and thyroid cGMP concentrations in male Wistar strain rats treated with estradiol benzoate (EB) (1 mg/kg, im twice a week) and nonselective NO-synthase inhibitor L-NAME (N-omega-nitro-L-arginine methyl ester) alone and with combination of these substances. We have found that L-NAME in a dose 100 mg/kg/day but not in a dose 50 mg/kg/day increased the serum thyroxine and testosterone levels and in the case of testosterone in a higher dose partially blocked its drop when administered simultaneously with EB. The serum thyrotropin levels significantly fell after L-NAME and EB treatment. The cGMP thyroid levels changed only slightly in groups treated EB and L-NAME alone and were significantly decreased in group treated with combination of these substances. The nitric oxide thus seems to be an important modulator of thyroid and testicular function. The cGMP activation cascade is not probably involved in the nitric oxide induced changes of thyroid function.