Effect of nitrogen dioxide exposure on cyclic GMP in rat lung

In vivo exposure of rats to 10 ppm nitrogen dioxide (NO2) for 6 h caused approx. 5-fold increase in the content of cyclic GMP in lung tissue. This increased cyclic GMP level lasted up to 24 h but returned to the normal level within 2 days, even when the NO2 exposure continued. This increase in the content of cyclic GMP of lung tissue by NO2 exposure was observed in both young and aged rats. There were no statistically significant changes in the content of cyclic AMP in lung tissue.     

Effect of benzodiazepines on cyclic GMP formation in rat cerebellar slices

Cyclic 3',5' guanosine monophosphate (cGMP) levels, stimulated in brain slices by ouabain, potassium, and sodium azide depolarization, have been found to be inhibited in a dose-dependent fashion by both behaviorally active and inactive benzodiazepines. ED50's for these benzodiazepines bear no relation to potencies established from receptor membrane binding studies; however, these values do correspond to ED50's calculated for several known membrane stabilizing agents tested in this system. The concentration of [3H]flunitrazepam necessary to saturate the benzodiazepine receptor in identical slice preparations is considerably lower than that needed to initiate inhibition of depolarization-induced cGMP stimulation. Some of the reported in vivo actions of benzodiazepines on cGMP formation may be the result of membrane stabilizing actions of the benzodiazepines or mediated indirectly.     

Effects of neuroleptic agents on cyclic GMP in rat cerebral cortex.

Cyclic guanosine 3' ,5'-monophosphate(cyclic GMP) levels were increased in incubated tissue slices from rat cerebral cortex in response to added cholinomimetic agents (carbachol and choline chloride) and neuroleptic compounds (chlorpromazine, 8-hydroxychlorpromazine, 7-hydroxychlorpromazine methiodide, haloperidol, thioridazine, chlorpromazine sulfoxide and promethazine). Calcium ion was required for this effect. Moreover, selected agents namely, 7,8-dihydroxychlorpromazine, 7,8-dimethoxychlorpromazine, chlorpromazine and clozapine prevented the rise in cyclic GMP induced by carbachol.     

Effects of L-NG-monomethyl arginine on the cyclic GMP formations in rat mesenteric arteries.

To evaluate the contribution of L-arginine as a precursor of the endothelium-derived relaxing factor (EDRF) on vascular cyclic GMP formation, we examined the effects of L-NG-monomethyl arginine (L-NMMA), and analog of L-arginine, on basal and acetylcholine (ACh)-, sodium nitroprusside (SNP)- and atrial natriuretic peptide (ANP)-induced cyclic GMP formations in rat mesenteric arteries. The mesenteric arteries were perfused with Krebs-Henseleit solution containing 0.2 mM isobutyl methyl xanthine. The effluents from the arteries were collected before and after infusions of graded doses of ACh, SNP or ANP in the absence or presence of 100 microM L-NMMA, and the levels of cyclic GMP were measured. Basal and ACh-induced cyclic GMP formations in the mesenteric arteries were significantly inhibited in the presence of L-NMMA, whereas a concomitant infusion of 300 microM L-arginine restored the inhibition of basal as well as ACh-induced cyclic GMP formations. L-NMMA did not affect SNP- and ANP-stimulated cyclic GMP formations, respectively. These results suggest that L-arginine is necessary for not only the stimulated cyclic GMP formation but also the basal cyclic GMP formation in the mesenteric arteries, whereas the SNP- and ANP-stimulated cyclic GMP formations in the arteries are independent of L-arginine.     

Effects of manganese on cyclic GMP levels in the rat ductus deferens

Summary Mn²⁺ and other divalent cations (Me²⁺) are capable of preventing contractile responses of smooth muscle to various stimuli. The effects of Mn²⁺, of other inhibitory Me²⁺ and of Ca²⁺ on basal and hormone-stimulated cyclic nucleotide levels were studied in the ductus deferens of the rat.In tissue segments that had been preincubated with no Me²⁺ added, Mg²⁺ (2 or 10 mM), Co²⁺, Ni²⁺ and Cd²⁺ (2 mM each) caused 2-fold elevations of the cyclic GMP level within 5 min, whereas Mn²⁺ and Ca²⁺ caused 7-and 5-fold elevations, respectively. Cyclic AMP levels were not significantly changed except for a 10–20% increase by Mn²⁺. Whereas Mn²⁺ caused a continuous rise of the cyclic GMP level over at least 10 min, the stimulatory effect of Ca²⁺ was most pronounced during the first minute. The effects of Ca²⁺ and Mn²⁺ were not additive. When Ca²⁺ was added with or after Mn²⁺ (2 mM each), the stimulatory effect of Mn²⁺ was depressed. Similarly, Mn²⁺ caused only a small increase in the cyclic GMP level of tissue incubated with Ca²⁺.With the hormonal stimuli, acetylcholine and noradrenaline (0.1 mM each), a dissociation of their effects on tissue tone and on the cyclic GMP level occurred. Whereas either stimulus caused about 2-fold elevation of the cyclic GMP in the presence of Mn²⁺ with or without Ca²⁺ present, contractile responses were prevented by Mn²⁺. In contrast, K⁺ at a high, depolarizing concentration, which increased the cyclic GMP level in the presence of Ca²⁺, had no effect on the cyclic nucleotide with Mn²⁺ added instead of Ca²⁺. Whereas hormone-induced elevations of the cyclic GMP level depended on the presence of Me²⁺, the effect of hydroxylamine (0.1 mM) to increase the level of this nucleotide in the absence of Me²⁺ was not augmented by Ca²⁺ or Mn²⁺.The present data indicate that hormone-induced elevations of the cyclic GMP level in the absence of extracellular Ca²⁺ do not promote contraction. The findings also suggest that hormones are capable of stimulating cyclic GMP formation by mechanisms other than hormone-induced increase in cytoplasmic Ca²⁺ concentration.Abbreviations cGMP cyclic - GMP guanosine 3:5-monophosphate - cAMP cyclic AMP, adenosine 3:5-monophosphate - Me²⁺ divalent cation(s) - EDTA ethylenediaminetetraacetic acid This work was supported by the Deutsche Forschungsgemeinschaft. A preliminary report was presented (Schultz and Schultz, 1976). The data have partially been taken from a dissertation submitted by K.D.S. to the University of Heidelberg in partial fulfillment of the requirements for the Ph. D. degree     

Effects of cyclic GMP and analogues on neurogenic transmission in the rat tail artery.

1. The effects of membrane permeable analogues of guanosine 3':5'-cyclic monophosphate (cyclic GMP), and of the NO donor, 3-morpholinosydnonimine-N-ethylcarbamide (SIN-1) were investigated on [3H]-noradrenaline release and neurogenic vasoconstriction in electrical field stimulated rat tail arteries. 2. Two 8-substituted analogues of cyclic GMP (8-bromoguanosine 3':5'-cyclic monophosphate; 8-bromo-cyclic GMP and 8-(4-chlorophenylthio)-guanosine 3':5'-cyclic monophosphate; 8-pCPT-cyclic GMP) concentration-dependently enhanced stimulation-induced [3H]-noradrenaline release. These prejunctional effects were antagonized by the cyclic AMP-dependent protein kinase (PKA) inhibitor N-[2-((3-(4-bromophenyl)-2-propenyl)-amino)-ethyl]-5 isoquinolinesulphonamide dihydrochloride (H-89; 100 nM) but not by the cyclic GMP-dependent protein kinase (PKG) inhibitors, Rp-8-bromoguanosine 3':5'-cyclic monophosphorothioate (Rp-8-bromo-cyclic GMPS; 10 microM) or Rp-8-(4-chlorophenylthio)-guanosine 3':5'-cyclic monophosphorothioate (Rp-8-pCPT-cyclic GMPS; 10 microM). 3. beta-Phenyl-1,N2-ethenoguanosine 3':5'-cyclic monophosphate (PET-cyclic GMP) had no effect on stimulation-induced [3H]-noradrenaline release but concentration-dependently decreased the stimulation-induced vasoconstriction. 4. The two 8-substituted cyclic GMP derivatives, PET-cyclic GMP and SIN-1, both decreased stimulation-induced vasoconstriction. In addition, SIN-1 relaxed rat tail arteries precontracted with phenylephrine (1 microM). The SIN-1 concentration-relaxation curve was shifted in parallel manner to the right by Rp-8-bromo-cyclic GMPS (10 microM) and Rp-8-pCPT-cyclic GMPS (10 microM) with no change in the maximum effect, showing that the relaxation was mediated by a cyclic GMP/PKG-dependent mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of endothelium on basal and on stimulated accumulation and efflux of cyclic GMP in rat isolated aorta.

1. The aim of this study was to examine the possible role of the release of guanosine 3':5'-cyclic monophosphate (cyclic GMP) into the extracellular space in the regulation of rat aortic cyclic GMP content. 2. Rat aortic segments incubated in physiological solution released cyclic GMP into the medium in a time-dependent manner. This release was greatly enhanced when intact instead of tissues without endothelium were used. After 120 min of observation, a maximal 33 fold difference in extracellular cyclic GMP content was detected. 3. Treatment of rat aortic preparations with either a Ca2+-free solution or methylene blue, both conditions known to inhibit endothelium-derived relaxing factor (EDRF)-mediated responses, markedly reduced the extracellular accumulation of cyclic GMP from tissues with but not without endothelium. 4. Endothelium-dependent vasodilators such as acetylcholine (10 microM) and carbachol (10 microM) greatly increased tissue cyclic GMP content, in a time-dependent manner in rat aortic preparations with endothelium, but only slightly in tissues without. Maximal increases in intact tissues were obtained after about 1 min of agonist contact and amounted to about 35 and 15 fold respectively, thereafter tissue cyclic GMP content rapidly declined. Histamine (10 microM) elicited only minor effects on tissue cyclic GMP content of both intact preparations and those without endothelium. 5. Acetylcholine (10 microM), carbachol (10 microM) and histamine (10 microM) stimulated a time-dependent release of the cyclic nucleotide into the incubation medium from tissues with endothelium. After 120 min of observation, extracellular accumulation of cyclic GMP from intact tissues was increased by about 2.6, 6.6 and 1.7 fold respectively. Carbachol and histamine induced only minor effects on release from tissues without endothelium. 6. Sodium nitroprusside (0.3 and 10 microM), a direct activator of soluble guanylate cyclase, induced a concentration-dependent accumulation of cyclic GMP in tissues with and without endothelium that was associated with a concentration-dependent accumulation of cyclic GMP in the extracellular space. Peak tissue cyclic GMP content reached similar levels in preparations with and without endothelium, while extracellular cyclic GMP levels were about two times greater when experiments were performed with intact compared to endothelium-denuded tissues. 7. Atriopeptin II, an activator of particulate guanylate cyclase, increased tissue cyclic GMP content by about 8 and 18 fold respectively in tissues with and without endothelium.(ABSTRACT TRUNCATED AT 400 WORDS)     

Cyclic AMP and cyclic GMP in the rat gastric mucosa

Summary Mice were given various 7-day treatments designed to reduce cerebral noradrenergic function. Following these treatments, alterations in the sensitivity of limbic forebrain adenylate cyclase to noradrenaline (NA), and in the locomotor response of the mice to dopaminergic and noradrenergic agonists were studied. An enhanced response of the NA-sensitive adenylate cyclase to 1-NA (10^–5 M), in comparison to control mice, was demonstrated after treatments producing a chronic reduction in stimulation of -adrenergic receptors (phenoxybenzamine 10 mg/kg per day), -adrenergic receptors (propranolol, 0.05% diet), all noradrenergic receptors (reserpine 5 mg/kg, followed by FLA-63, 25 mg/kg per day), and dopaminergic as well as noradrenergic receptors (chlorpromazine, 5 mg/kg per day). Sensitivity of the NA-stimulated adenylate cyclase was not altered by chronic treatment with FLA-63 alone as a 0.05% diet. However, none of the chronic treatments except chlorpromazine administration increased the locomotor activity recorded for 2 h following apomorphine (1 mg/kg, s.c.) and none of the treatments altered the locomotor activity recorded in the 2 h following administration of the -adrenergic agonist clonidine (1 mg/kg, i.p.), or a combination of apomorphine (1 mg/kg, s.c.) plus clonidine (1 mg/kg, i.p.) The results support the hypothesis that noradrenergic stimulation plays a role secondary to that of dopamine in the production of locomotor activity.     

Effect of cholecystokinin-pancreozymin on the nitric oxide synthase activity and cyclic GMP level in rat pancreatic tissue

In pancreatic cells, NO formation is associated with increased levels of cGMP and endocrine/ exocrine secretion. In the present study, the role of NO in the regulation of exocrine secretion was investigated in rat pancreatic tissues. Treatment of rat pancreatic tissue with cholecystokinin-pancreozymin (CCK-PZ) resulted in an significant increase in arginine conversion to citrulline, the amount of nitrite/nitrate, the release of amylase, and the level of cGMP. Furthermore, CCK-PZ-stimulated increase of amylase release and conversion of arginine to citrulline transformation were counteracted by the inhibitor of NO synthase, N^G-nitro-L-arginine methyl ester. The results on the time course of CCK-PZ-induced citrulline formation and rise of cGMP level indicate that NO synthase and guanylate cyclase are activated within the first seconds of stimulation. The kinetics of citrulline accumulation correlate well with those of cGMP rise, which further confirms the conclusion that NO mediates the response to CCK-PZ by cGMP.     

Carbachol and dibutyryl cyclic GMP on the vulnerability to ventricular fibrillation in rat isolated hearts.

The hypothesis that elevation of intracellular guanosine 3':5' cyclic monophosphate (cyclic GMP) concentrations may increase electrical stability of the myocardium was examined by determination of ventricular fibrillation thresholds (VFT) on isolated perfused hearts of the rat. Hearts were paced to circumvent any complicating effects of bradycardia. Using this system, carbachol produced a concentration-related reduction in VFT. The reduction in VFT produced by carbachol was not significantly modified by a high concentration of atenolol (10(-5)M), indicating that the increased vulnerability to ventricular fibrillation was not an indirect consequence of catecholamine release from intramyocardial stores. Atropine (10(-6)M) blocked the carbachol-induced reduction in VFT. At the concentrations of carbachol used to reduce VFT, myocardial cyclic GMP concentrations were also elevated. The dibutyryl analogue of cyclic GMP (10(-4)M) mimicked the effect of carbachol in reducing VFT. Carbachol potentiated the adrenaline (3 X 10(-7)M)-induced reduction in VFT.     

Effect of cyanide on nitrovasodilator-induced relaxation, cyclic GMP accumulation and guanylate cyclase activation in rat aorta

The effects of sodium cyanide on relaxation, increases in cyclic GMP accumulation and guanylate cyclase activation induced by sodium nitroprusside and other nitrovasodilators were examined in rat thoracic aorta. Cyanide abolished nitroprusside-induced relaxation and the associated increase in cyclic GMP levels. Basal levels of cyclic GMP and cyclic AMP were also depressed. Reversal of nitroprusside-induced relaxation by cyanide was independent of the tissue level of cyclic GMP prior to addition of cyanide. Incubation of nitroprusside with cyanide prior to addition to aortic strips did not alter the relaxant effect of nitroprusside. Sodium azide-, hydroxylamine-, N-methyl-N'-nitro-N-nitrosoguanide-, nitroglycerin- and acetylcholine-induced relaxations and increased levels of cyclic GMP were also inhibited by cyanide. Relaxations induced by nitric oxide were also inhibited by cyanide, although the relaxation with the low concentration of nitric oxide employed was not accompanied by detectable increases in cyclic GMP. Relaxation to 8-bromo-cyclic GMP was essentially unaltered by cyanide; however, isoproterenol-induced relaxation was inhibited. Guanylate cyclase in soluble and particulate fractions of aorta homogenates was activated by nitroprusside and the activation was prevented by cyanide. The present results suggest that cyanide inhibits nitrovasodilator-induced relaxation through inhibition of guanylate cyclase activation; however, cyanide may also have nonspecific effects which inhibit relaxation.     

Effect of morphine on the tissue cyclic AMP and cyclic GMP content in two strains of mice

The effect of morphine on the cyclic (c) AMP and cyclic (c) GMP concentrations in several organs, and its reversal by naloxone have been investigated in C57BL and DBA strains of mice. Morphine increased the cAMP contents in lungs and muscle, and the cGMP contents in lungs, intestine, heart, liver and muscle in a naloxone-reversible way in C57BL mice only. This is consistent with our previous observation that morphine increased plasma cyclic nucleotide levels in C57BL mice, whereas such an increase was marginal in the DBA strain. These results show that there is a strain difference in the effect of morphine on tissue cyclic nucleotide contents and the possible origin of the plasma cyclic nucleotides which are increased by morphine.     

Effect of sodium nitroprusside and 8-bromo cyclic GMP on nerve-mediated and acetylcholine-evoked secretory responses in the rat pancreas

The effects of sodium nitroprusside (SNP) and 8-bromo-guanosine 3'5' cyclic monophosphate (8-Br-cyclic GMP) on nerve-mediated and acetylcholine (ACh)-evoked amylase secretion, tritiated choline ([3H]-choline) release and on intracellular free calcium concentration ([Ca2+]i) in the isolated rat pancreas were investigated. Electrical field stimulation (EFS; 10 Hz) and ACh (1 x 10(-5) M) caused large increases in amylase output from pancreatic segments. The response to ACh was blocked by atropine (1 x 10(-5) M) whereas the EFS-evoked response was markedly reduced but not abolished. In contrast, pretreatment with tetrodotoxin (1 x 10(-6) M) abolished the secretory effect of EFS. Either SNP (1 x 10(-3) M) or 8-Br-cyclic GMP (1 x 10(-4) M) inhibited amylase secretion compared to basal. Combining either SNP or 8-Br-cyclic GMP with EFS resulted in a marked decrease in amylase output compared to EFS alone. In contrast, either SNP or 8-Br-cyclic GMP had no significant effect on the amylase response to ACh. When extracellular Ca2+ concentration ([Ca2+]o) was elevated from 2.56 mM to 5.12 mM, SNP failed to inhibit the response to EFS. EFS stimulated the release of 3H from pancreatic segments preloaded with [3H]-choline. Either SNP or 8-Br-cyclic GMP had no effect on basal 3H release but significantly reduced the EFS-evoked response. In fura-2 loaded acinar cells, SNP elicited a small decrease in [Ca2+]i compared to basal and had no effect on the ACh-induced [Ca2+]i peak response. Nitric oxide may modulate the release of endogenous neural ACh in response to EFS in the rat pancreas.     

Novel kainic acid analogues. Effects on cyclic GMP content of adult rat cerebellar slices

On the basis of previous electrophysiological studies, it has been proposed that there are three main classes of excitatory amino acid receptor in the mammalian central nervous system, which are activated preferentially by kainic acid, quisqualic acid and N-methyl-D-aspartate respectively. Although the pharmacology of the N-methyl-D-aspartate receptor has been investigated extensively, potent and selective ligands which act at the kainate or quisqualate sites are lacking. In this study, we report that a number of novel kainate analogues possess either agonist or antagonist activity in a system which permits investigation of receptor-mediated coupled responses, viz. the ability of excitatory amino acids to elevate cyclic GMP concentrations in incubated cerebellar slices prepared from the adult rat. The data reported here provide some clues as to the likely structural requirements for developing effective kainate antagonists.     

Regional cyclic GMP content in incubated tissue slices of rat brain

Incubated tissue slices from different regions of the rat brain contained cyclic guanosine 3′,5′-monophosphate (cyclic GMP) in the following descending order of content: cerebellum hypothalamus striatum thalamus-midbrain brain stem hippocampus cerebral cortex. Cholinomimetic agents at 10^?5 M (carbamylcholine, pilocarpine, acetylcholine and eserine) and papaverine at 10^?4 M significantly elevated cyclic GMP accumulation in the cerebral cortex. Three min incubation with carbamylcholine (10^?5 M) did not increase cyclic nucleotide accumulation in the remaining brain regions.     

Effect of nitric oxide on integrity, blood flow and cyclic GMP levels in the rat gastric mucosa: modulation by sialoadenectomy.

1. The effects of the nitrosothiol, S-nitroso N-acetylpenicillamine (SNAP) which liberates nitric oxide (NO), on ethanol-mediated gastric damage, blood flow and cyclic GMP levels in siaoloadenectomized (SALX) rats have been investigated. 2. Intraluminal instillation of ethanol (5-50% w/v) dose-dependently induced haemorrhagic damage and decreased NO synthase activity in the gastric mucosa. Both the extent of mucosal damage and inhibition of NO synthase activity were exacerbated in SALX rats. 3. Epidermal growth factor administration (5 and 10 micrograms kg-1, s.c.) reduced mucosal damage but did not restore NO synthase activity in ethanol-treated SALX rats. 4. SNAP infusion (0.01-1.0 micrograms kg-1 min-1, i.v.) attenuated haemorrhagic damage in ethanol-treated rats. The reduction in mucosal damage was significantly greater in SALX rats. 5. SNAP administration also caused an increase in gastric mucosal blood flow and cyclic GMP levels in control rats and both responses were augmented in SALX animals. 6. These data suggest that SALX is associated with increases in mucosal susceptibility to ethanol-mediated damage and reduces mucosal NO synthase activity. Epidermal growth factor does not appear to influence mucosal NO synthase in ethanol-treated rats. Furthermore, SALX augments the responsiveness of the gastric mucosa to NO administration. Therefore, factors from the salivary glands influence gastric NO formation and mucosal responsiveness to a NO donor.     

Effect of in vivo nitroglycerin therapy on endothelium-dependent and independent vascular relaxation and cyclic GMP accumulation in rat aorta

Vascular relaxation by the organic (nitroglycerin) and inorganic (sodium nitroprusside) nitrovasodilators and the endothelium-dependent vasodilators (acetylcholine and histamine) has been associated with cyclic GMP accumulation. Tolerance to vasodilation by nitroglycerin commonly occurs following prolonged exposure to nitroglycerin. This study investigates the effects of in vivo nitroglycerin therapy on vascular relaxation and cyclic GMP accumulation induced by the nitrovasodilators and the endothelium-dependent vasodilators. Rats were injected with nitroglycerin or the propylene glycol diluent control for 4-7 days. Thoracic aortas from the nitroglycerin-treated rats were 750-fold less sensitive to the relaxant effects of nitroglycerin. In contrast, these aortas were only threefold less sensitive to the relaxant effects of sodium nitroprusside, while the maximum relaxation to acetylcholine and histamine was depressed by 50 and 41%, respectively. Desensitization to relaxation was associated with reduced cyclic GMP elevations to all the vasodilators. Relaxation to 8-bromo cyclic GMP, dibutyryl cyclic AMP, or diltiazem was unaffected by nitroglycerin therapy. Tolerance was also associated with an increased sensitivity to the contractile effects of low concentrations of norepinephrine. This increased sensitivity to norepinephrine was associated with a decrease in cyclic GMP levels. The present results suggest that: (1) desensitization to nitroglycerin, sodium nitroprusside, acetylcholine, and histamine by nitroglycerin therapy may be at the level of cyclic GMP accumulation; (2) cyclic GMP is the common mediator of relaxation induced by the nitro- and endothelium-dependent vasodilators; (3) the mechanisms involved in the activation of guanylate cyclase and relaxation by sodium nitroprusside, acetylcholine, and histamine are probably different than those of nitroglycerin; and (4) cyclic GMP may be acting as a physiological negative feedback signal in agonist-induced contraction.     

Nitric oxide-mediated relaxation without concomitant changes in cyclic GMP content of rat proximal colon.

1. We studied the relation of nitric oxide-mediated relaxation of longitudinal muscle to changes in cyclic GMP content of the tissue in the proximal colon of rats. 2. Dimethylphenylpiperazinium (DMPP) and electrical field stimulation (EFS) induced nitric oxide-mediated relaxation of the segments with a concomitant increase in cyclic GMP content. 3. LY 83583 and methylene blue, soluble guanylyl cyclase inhibitors, significantly inhibited the stimulatory effects of DMPP and EFS on the cyclic GMP content, but did not affect the relaxant responses of the segments to DMPP and EFS. 4. Rp-8 bromo cyclic GMPS, an inhibitor of cyclic GMP-dependent protein kinase had no effect on DMPP- and EFS-induced relaxation. 5. These data strongly suggested that nitric oxide-mediated relaxation of the rat proximal colon is not associated with change in cyclic GMP content of the tissue.