Effect Of Dibutyryl Cyclic AMP Research Articles

Dibutyryl cyclic AMP has epileptogenic potential in the hippocampus of freely behaving rats: a combined EEG-intracerebral microdialysis study

The effects of dibutyryl cyclic AMP were studied with the combined EEG-intracerebral microdialysis technique in the hippocampus of freely behaving rats. It was found that intrahippocampal microdialysis with this drug produced epileptiform EEG events associated with limbic type behavioral seizures. The dibutyryl cyclic AMP-induced seizures developed with a long latency, and persisted for a prolonged period even after the removal of the drug from the microdialysis fluid. Similar EEG or behavioral manifestations did not occur during intrahippocampal microdialyses with artificial cerebrospinal fluid or ATP solutions. These data suggest that in the hippocampus, in vivo, the cyclic AMP second messenger system may be involved in potentially epileptogenic excitatory processes.

Cyclic AMP inhibition of lipopolysaccharide-induced restriction of Legionella pneumophila growth in macrophage cultures.

The mechanism of the effects of lipopolysaccharide (LPS) on macrophages in terms of replication of intracellular facultative bacteria is unclear. It was found in the present study that the anti-Legionella pneumophila activity induced by LPS in macrophages from susceptible A/J mice was reversed in vitro by dibutyryl cyclic AMP (DcAMP). A 24-h pretreatment of murine thioglycolate-elicited macrophages with LPS resulted in an enhanced ability of these cells to inhibit the intracellular growth of L. pneumophila. This anti-L. pneumophila activity of macrophages induced by LPS was inhibited when DcAMP (10(-3) to 10(-5) M) was present during preincubation with LPS. The addition of DcAMP to the cultures was more effective before LPS treatment than after treatment. The effect of DcAMP was dose dependent. The secretion and production of acid phosphatase by LPS-activated macrophages were also inhibited by the addition of DcAMP before LPS treatment. Furthermore, the anti-L. pneumophila activity of macrophages induced by LPS could also be reversed in vitro by treatment with prostaglandin E2, colchicine, isoproterenol, theophylline, or hydrocortisone, all of which are known to increase the intracellular levels of cyclic AMP in various tissues. These observations indicate that the anti-L. pneumophila activity induced by LPS treatment can be modified by mechanisms involving cyclic nucleotide metabolism.

Somatostatin inhibition of gastrin gene expression: involvement of pertussis toxin-sensitive and -insensitive pathways

These studies were performed to determine the intracellular pathways involved in regulating gastrin gene expression. The inclusion of 10 −4 M forskolin or 10 −4 M dibutyryl cyclic AMP (DBcAMP) in incubation medium containing dog antral mucosa resulted in 249% and 323% increases, respectively, in gastrin mRNA levels. The stimulatory effects of forskolin and DBcAMP were both inhibited significantly by 10 −6 M somatostatin. Preincubation of antral mucosa with pertussis toxin nearly abolished the inhibitory effects of somatostatin on gastrin mRNA stimulated by forskolin, but had no effect following DBcAMP. To examine whether calcium-dependent pathways might be involved in regulating gastrin gene expression, antral mucosa was incubated with increasing concentrations of calcium or the ionophore ionomycin. Both agents produced only modest increases in gastrin mRNA, which were abolished by the addition of somatostatin to the incubation medium. These studies indicate that somatostatin appears to inhibit gastrin gene expression through mechanisms involving both pertussis toxin-sensitive and -insensitive pathways.

Mechanisms underlying the inhibitory effect of dibutyryl cyclic AMP in vascular smooth muscle

The mechanism by which dibutyryl cyclic AMP (db-cAMP) induces vasodilatation was examined in isolated rat aorta. The contraction induced by norepinephrine (NE) was more sensitive to the inhibitory effect of db-cAMP than that induced by high K +, and the contraction induced by lower concentrations of each stimulant was more sensitive to db-cAMP than that induced by higher concentrations. Db-cAMP at 10 μM inhibited the increases in muscle tension and cytosolic Ca 2+ level ([Ca 2+] i) without changing the [Ca 2+] i-tension relationship, suggesting that the inhibitory effect is mainly due to a decrease in [Ca 2+] i. A higher concentration (300 μM) of db-cAMP inhibited muscle tension more strongly than [Ca 2+] i suggesting that db-cAMP decreases Ca 2+ sensitivity of contractile elements. In contrast, 10 μM verapamil inhibited the NE-stimulated [Ca 2+] i more strongly than the NE-induced contraction. The verapamil-insensitive portion of the NE-stimulated [Ca 2+] i and contraction was inhibited by db-cAMP, suggesting that db-cAMP and verapamil act by different mechanisms. In Ca 2+-free solution, 1 μM NE induced transient increases in muscle tension and [Ca 2+] i. The transient contraction was inhibited by 1 mM db-cAMP more strongly than [Ca 2+] i. An activator of adenylate cyclase, forskolin, showed inhibitory effects similar to those of db-cAMP. The inhibitory effects of db-cAMP and forskolin were inversely proportional to [Ca 2+] i before the addition of these inhibitors. These results suggest that db-cAMP inhibits smooth muscle contraction by decreasing [Ca 2+] i and the Ca 2+ sensitivity of contractile elements, and that both of these effects are stronger when [Ca 2+] i is lower.

Transcriptional and post-transcriptional effects of glucose on liver phosphoenolpyruvate-carboxykinase gene expression.

The present study investigates the effect of glucose on the gene expression of the hepatic glucoregulatory enzyme, phosphoenolpyruvate carboxykinase (PPrvck). By use of hepatocytes in culture and FAO hepatoma cells it could be demonstrated that glucose suppressed the effect of dibutyryl cyclic AMP (Bt2cAMP), glucocorticoids or both, to increase PPrvck mRNA and consequently PPrvck enzyme activity. Glucose had a dual effect; it reduced PPrvck gene transcription and it accelerated the rate of PPrvck mRNA degradation. The effect was specific for glucose, as glucose-related carbohydrates such as mannose, galactose and sorbitol were without effect on PPrvck mRNA. The repressive effect of glucose was limited to certain proteins; glucose had no effect on Bt2cAMP and glucocorticoid provoked induction of tyrosine aminotransferase (TAT). Also the pattern of mRNA in vitro translation products was virtually unaffected when FAO hepatoma cells were incubated either in the presence or absence of glucose, demonstrating the specificity of the effect of glucose on gene expression of selected proteins. In FAO hepatoma cells and in hepatocytes in culture, insulin, like glucose, also decreased PPrvck mRNA. While the effect of glucose and insulin was additive in FAO hepatoma cells, in primary hepatocytes in culture an effect of glucose by itself on PPrvck mRNA could only be demonstrated in the absence of insulin. Correspondingly also in vivo, the effect of glucose was demonstrated in the absence of insulin (provoked by streptozotocin diabetes); glucose application reduced the amount of hepatic PPrvck mRNA. To summarize, glucose is capable of suppressing the effect of glucocorticoids and Bt2cAMP on increasing the PPrvck mRNA level. The carbohydrate reduces the rate of PPrvck gene transcription and accelerates the rate of PPrvck mRNA degradation. While in FAO hepatoma cells the effect is evident in the presence of insulin, in hepatocytes in culture the effect of glucose cannot be demonstrated in the presence of insulin, questioning its role under physiological conditions.

Effects of cyclic AMP and phorbol ester on transepithelial electrical resistance of Sertoli cell monolayers in two-compartment culture

The effects of dibutyryl cyclic AMP ((Bu) 2cAMP) and phorbol ester (TPA), in the absence or presence of follicle-stimulating hormone (FSH) and/or testosterone, on the development of tight junctions by immature rat Sertoli cells (Sc) were investigated in vitro using the two-compartment culture system. The tight junction status was evaluated by repeated measurements of transepithelial electrical resistance (TER). Untreated cell monolayers developed stable TER of approximately 120 Ωcm 2 during 3 days of culture. Continuous presence of FSH (200 ng/ml) from day 1 onward significantly increased the TER up to approximately 300 Ωcm 2 after a transient (24–36 h) delay. The initial delay was prolonged to 3–4 days by the addition of 1-methyl-3-isobutylxanthine (MIX) (0.2 mM), whereas the subsequent increase of TER was significantly potentiated by the concomitant presence of testosterone (10 μM). Cholera toxin (CHT; 10 ng/ml) and forskolin (FR; 50 μM) mimicked these FSH effects. (Bu) 2cAMP, at concentrations which maximally stimulated immunoactive inhibin secretion (100–500 μM), inhibited the initial TER increase and significantly decreased the TER level when added on days 1 and 5 of culture, respectively. In contrast, low concentrations of (Bu) 2cAMP (4–20 μM) consistently stimulated the TER development, mimicking the stimulatory phase of FSH action. TPA (100 nM) alone had no effect on TER development, but potentiated the stimulatory effect of testosterone in a manner similar to FSH, CHT, FR or low concentrations of (Bu) 2cAMP. These results demonstrate, for the first time, a concentration-dependent, dual effect of exogenous cAMP on the Sc function. Moreover, our data suggest that, at least in vitro, FSH regulates the formation of inter-Sc tight junctions via a cAMP-mediated mechanism and that protein kinase C may modulate the testosterone-, but not FSH-dependent development of tight junctions by immature Sc.

Changes in cell cycle and chromatin distribution in C6 glioma cells treated by dibutyryl cyclic AMP.

C6 glioma cells in culture were treated with 1 mM dibutyryl cyclic AMP (Db-cAMP) for 5, 8, 24 and 72 h. The cells were labelled with [3H]-thymidine before either the end, or the beginning, of the Db-cAMP treatment. The cell cycle passage was monitored by the simultaneous determination of DNA content and DNA synthesis in propidium iodide stained autoradiograms. The data revealed an early (t less than or equal to 3-8 h) and moderate inhibitory effect of Db-cAMP on all phases of the cell cycle except mitosis; some cells (2%) were completely blocked in the S phase. Later (8 less than t less than 24-72 h), the cycling of a substantial part of the population became inhibited in G1 phase. Microdensitometric texture analysis of Feulgen-stained nuclei, performed 24 h after administration of Db-cAMP, showed a higher inhomogeneity of the DNA distribution in cell nuclei, caused by the condensation of a part of the chromatin. This may reflect either changes in genome expression taking part in the process of cAMP induced differentiation or transit of some cells into quiescent G0 or S0 phases.

Somatostatin partially impedes the stimulatory effects of thyrotrophin-releasing hormone and dibutyryl cyclic AMP on prolactin release: prolactin release through multiple routes

Patterns of prolactin release were examined using stimulating and inhibiting agents. Primary cultured pituitary cells primed with oestrogens were used for perifusion experiments. TRH (100 nmol/l) increased the peak prolactin concentration to 360% of the basal concentration, while TRH, under inhibition by 1 nmol somatostatin/l, raised the peak prolactin concentration to 185% of the basal levels. When the somatostatin concentration was increased to 10, 100 and 1000 nmol/l, TRH still stimulated prolactin release to 128%, 121% and 140% respectively, indicating that concentrations of somatostatin of 10 nmol/l or higher did not further suppress the stimulatory effect of TRH. TRH (1 mumol/l) stimulated prolactin release under the influence of 0 (control), 1, 10, 100 and 1000 nmol dopamine/l (plus 0.1 mmol ascorbic acid/l) to 394, 394, 241, 73 and 68% of the basal concentration respectively, showing that the dopamine concentrations and peak prolactin concentrations induced by TRH have an inverse linear relationship in the range 1-100 nmol dopamine/l. The stimulatory effect of dibutyryl cyclic AMP (dbcAMP) on prolactin release was also tested. The relationship between dbcAMP and somatostatin was similar to that between TRH and somatostatin. When adenohypophyses of male rats were used for perifusion experiments, somatostatin (100 nmol/l) did not inhibit basal prolactin release from the fresh male pituitary in contrast with the primary cultured pituitary cells, but dopamine (1 mumol/l) effectively inhibited prolactin release. In conclusion, (1) oestrogen converts the somatostatin-insensitive route into a somatostatin-sensitive route for basal prolactin release, (2) TRH-induced prolactin release passes through both somatostatin-sensitive and -insensitive routes, (3) dopamine blocks both somatostatin-sensitive and -insensitive routes and (4) cAMP activates both somatostatin-sensitive and -insensitive routes.

Effects of dibutyryl cyclic AMP, ouabain, and xanthine derivatives on crossbridge kinetics in rat cardiac muscle.

In a previous communication, we showed that beta-adrenergic stimulation of cardiac muscles was associated with an increase in the rate of cycling of crossbridges as measured by perturbation analysis in the frequency domain. In this analysis, the frequency at which dynamic stiffness is a minimum (fmin) is taken as a measure of the rate of crossbridge cycling. In this paper, we test the hypothesis that the beta-adrenergic receptor-induced increase in crossbridge cycling rate is mediated by elevation of the intracellular level of cyclic AMP. The approach taken is to compare the effects on fmin in rat papillary muscles during Ba(2+)-activated contractures of 1) an agonist of cyclic AMP that can easily penetrate the cell, namely, dibutyryl cyclic AMP, 2) agents that block cyclic AMP phosphodiesterase, namely, the xanthine derivatives isobutylmethylxanthine and caffeine, and 3) an inotropic agent that does not affect the intracellular level of cyclic AMP, namely, ouabain. Our results showed that dibutyryl cyclic AMP at a dose of 5 mM has the same actions as beta-adrenergic stimulation: it potentiated the isometric twitch force, reduced the time to peak tension and time to half relaxation, and shifted fmin by a factor of 1.8 +/- 0.1 (n = 5). Isobutylmethylxanthine at up to 1.1 mM also acted in the same manner, increasing fmin by a factor of 1.8 +/- 0.2 (n = 6), but ouabain, at a dose (0.03 mM) sufficient to potentiate twitch force by 40 +/- 2% (n = 4), was without effect on the time course of the twitch nor was fmin changed (n = 4). Our findings support the hypothesis that a beta-adrenergic receptor-mediated increase in crossbridge cycling rate is due to an increase in intracellular cyclic AMP level and illustrate the usefulness of the frequency domain analysis approach in the analysis of the mechanism of action of inotropic agents.

Effects of dibutyryl cyclic AMP on ventricular vulnerability during atrioventricular block in dog

The effects of dibutyryl cyclic AMP (DBcAMP) on ventricular vulnerability during complete atrioventricular block (CAVB) were studied one week after transarterial electrical ablation of the AV junction in 18 closed-chest dogs. All dogs exhibited CAVB and a stable ventricular escape rhythm with a mean cycle length of 1812 +/- 638 ms. After the administration of DBcAMP at a rate of 0.1 mg/kg/min for 30 min, the ventricular cycle length was significantly shortened, and the QTc interval was slightly prolonged, although the QT interval did not change. The ventricular fibrillation threshold after the administration of DBcAMP was significantly increased (from 12.2 +/- 3 84 to 18.4 +/- 5.08 mA, p less than 0.01). Thus, it was demonstrated that DBcAMP exhibited suppressive effects on the ventricular vulnerability in the experimentally induced CAVB.

PIVKA II分泌に対する dibutyryl cyclic AMPの影響

PIVKA II分泌に対する dibutyryl cyclic AMPの影響

Herpes Simplex Virus Type 1 Infection of Rat Astrocytes in Primary Culture: Effects of Dibutyryl Cyclic AMP

Monolayer cultures of primary rat astrocytes grown with or without dibutyryl cyclic AMP (dBcAMP) for two weeks or longer were infected with round plaque-forming (Rd) or syncytia-forming (Syn) variants of herpes simplex virus type 1 (HSV-1). Infection with HSV-1 did not stimulate synthesis of glial fibrillary acidic protein (GFAP) or alter the general organization of the intermediate (glial) filaments in astrocyte cultures. However, the dBcAMP-treated astrocytes produced 10- to 100-fold lower titers of cell-free progeny HSV-1 than the untreated astrocyte cultures. Radiolabeled amino acid or glucosamine incorporated into acid precipitable cellular or viral glycoproteins was decreased by 10-25% in dBcAMP-treated astrocytes. Distinctive cell-rounding or syncytial cytopathology was produced by HSV-1 strains infecting untreated astrocytes, but the infected dBcAMP-treated astrocytes displayed only cell-rounding cytopathology. The dBcAMP-related effects on HSV-1 infection were specific to primary astrocyte cultures; they were not observed in HSV-1-infected human fibroblast cultures treated with dBcAMP. Comparison of HSV-1 infection of untreated versus dBcAMP-treated astrocytes suggests that the dBcAMP-induced "reactive" or differentiated state of the astrocyte can affect expression of virus-induced cytopathology and virus-specific polypeptide synthesis. The dBcAMP-treated primary astrocyte culture may afford a non-neoplastic, differentiated in vitro system for studying HSV-neural cell interactions.

P-458 - The inhibitory effects of dibutyryl cyclic AMP on cytosolic Ca2+ levels and contraction in smooth muscle of rat aorta

P-458 - The inhibitory effects of dibutyryl cyclic AMP on cytosolic Ca2+ levels and contraction in smooth muscle of rat aorta

The Effect of Dibutyryl-Cyclic Amp on the Ciliary Activity of Respiratory Epithelium from Patients with Cystic Fibrosis G DI Benedetto

The Effect of Dibutyryl-Cyclic Amp on the Ciliary Activity of Respiratory Epithelium from Patients with Cystic Fibrosis G DI Benedetto

Effects of DBcAMP on exercise capacity in patients with and without chronic heart failure

The acute effects of vasodilation on exercise capacity in cardiac patients with (group 1) and without (group 2) congestive heart failure were studied using dibutyryl cyclic AMP (DBcAMP). Exercise was performed on an upright bicycle ergometer using a graded protocol. DBcAMP increased cardiac output and decreased pulmonary capillary wedge pressure and systemic vascular resistance both at rest and during maximal exercise in these two groups. However, before and after DBcAMP neither exercise duration (371 ± 52 seconds vs. 388 ± 44, NS, in group 1, 645 ± 148 vs. 635 ± 143 seconds, NS, in group 2, respectively) nor maximal oxygen consumption (12.8 ± 2.3 ml/kg/min vs. 13.1 ± 1.6, NS, in group 1, 20.3 ± 1.4 vs. 20.1 ± 1.5, NS, in group 2, respectively) was improved. In both groups the arteriovenous oxygen differences were lower at rest and during exercise performed while on DBcAMP than in the control state. In group 2 patients excess vasoconstriction mediated by abnormally increased neurohormonal activities or edema were absent. Failure of the vasodilator to increase exercise capacity is probably due to nonspecific vasodilation and maldistribution of increased cardiac output, and not to tight vasoconstriction or narrowed arteriolar lumen.

An experimental study of cardio pulmonary-cerebral resuscitation (CPCRfProtective effects of dibutyryl cyclic AMP (DBcAMP) on the brain

An experimental study of cardio pulmonary-cerebral resuscitation (CPCRfProtective effects of dibutyryl cyclic AMP (DBcAMP) on the brain

Effect of dibutyryl cyclic AMP on bile acid synthesis in biliary-drained rats

Effect of dibutyryl cyclic AMP on bile acid synthesis in biliary-drained rats

Synthesis and Accumulation of Hyaluronic Acid and Proteoglycans in the Mouse Cumulus Cell-oocyte Complex during Follicle-stimulating Hormone-induced Mucification

In most mammalian ovaries, the cumulus cell-oocyte complex (COC) expands at the time of ovulation by depositing an extensive extracellular matrix between the cumulus cells. This phenomenon can be reproduced in vitro by culturing COCs with follicle-stimulating hormone (FSH) and serum. Biosynthesis of hyaluronic acid (HA) and proteoglycans by mouse COCs in vitro was studied using [3H]glucosamine and [35S]sulfate as metabolic precursors. Radiolabeled complex carbohydrates were analyzed by ion exchange chromatography, specific enzyme digestion followed by high performance liquid chromatography, and gel filtration. The specific activities of [3H]hexosamines in the labeled molecules were determined by measuring the incorporation of 3H and 35S into chondroitin 4-sulfate disaccharides. When COCs were stimulated with FSH, HA biosynthesis increased 20-30-fold between 3-12 h later when expansion occurs, reaching a maximum rate of approximately 780 pmol (as glucosamine)/COC/h compared with the unstimulated rate of approximately 26 pmol/COC/h. The final concentration of HA in the expanded COC was calculated to be approximately 250 micrograms/ml. The effects of dibutyryl cyclic AMP (Bt2cAMP) on COC expansion and HA synthesis were similar to those of FSH, suggesting that the effects of FSH are mediated by cAMP. However, FSH significantly decreased the specific activity of the incorporated hexosamines while Bt2cAMP did not. Serum is necessary for the accumulation of HA in the COC matrix. HA synthesis in FSH-stimulated COCs was as high or higher in the absence of serum, but most was recovered in the medium and not in the COC matrix. The molecular size of the HA was greater than 2 million dalton in either case, suggesting that the serum did not alter physical properties of HA. Stimulation of proteoglycan biosynthesis by either FSH or Bt2cAMP was less pronounced (three to four times control) than for HA and was sustained throughout an 18-h culture period. A reduction of 80% in the deposition of newly synthesized PGs in the COC matrix by 0.5 mM beta-xyloside treatment did not affect the expansion of the cumulus.

Regulation of Expression of the Gene Encoding the Major Surfactant Protein (SP-A) in Human Fetal Lung in Vitro: Disparate effects of glucocorticoids on transcription and on mRNA stability

Abstract We previously observed that dexamethasone had a biphasic effect on the levels of mRNA encoding the major surfactant protein (SP-A) in human fetal lung in vitro; at concentrations of 10(-10) and 10(-9) M, dexamethasone caused an increase in the levels of SP-A mRNA, whereas at concentrations of greater than 10(-8) M, the steroid had a pronounced inhibitory effect on SP-A mRNA levels. It was also found that dexamethasone antagonized the stimulatory effect of dibutyryl cyclic AMP (Bt2cAMP) on SP-A mRNA levels in human fetal lung in vitro. It was our objective, in the present study, to characterize further the effects of dexamethasone and Bt2cAMP on SP-A mRNA levels in human fetal lung tissue and to determine whether such effects are associated with comparable changes in the transcriptional activity of the SP-A gene. We found that the action of dexamethasone (10(-7) M) to reduce the levels of SP-A mRNA in control and Bt2cAMP-treated fetal lung explants was evident within 2 h of its addition to the culture medium; SP-A mRNA was reduced to barely detectable levels in control and in Bt2cAMP-treated tissues after 24 h of dexamethasone treatment. The action of dexamethasone to reduce SP-A mRNA levels was not prevented by co-incubation with either actinomycin D or cycloheximide. In contrast to its dose-related biphasic effects on the levels of SP-A mRNA, we found that dexamethasone caused a dose-dependent stimulation of SP-A gene transcription. Bt2cAMP also increased the transcriptional activity of the SP-A gene in the human fetal lung in vitro. In fetal lung explants incubated in the presence of dexamethasone plus Bt2cAMP, a synergistic induction of SP-A gene transcription was observed at concentrations of dexamethasone of 10(-9)-10(-7) M. Our findings are indicative that the stimulatory effects of dexamethasone (10(-10)-10(-9) M) on SP-A mRNA levels are reflective of a stimulatory effect of the steroid on SP-A gene transcription, whereas the inhibitory effects of dexamethasone (10(-7) M) on SP-A mRNA levels are the result of a dominant effect of the steroid in elevated concentrations to reduce SP-A mRNA stability.

Effects of dibutyryl cyclic AMP on hemodynamics and plasma catecholamine concentrations during ammonium chloride-induced metabolic acidosis in anesthetized dogs

We investigated, using anesthetized dogs, the effect of dibutyryl cyclic AMP (db-cAMP), a derivative of cyclic AMP (cAMP), on cardiovascular variants and plasma catecholamines during metabolic acidosis. These effects were also compared with those of dopamine. The db-cAMP and dopamine were infused at 200 and 20 micrograms/kg.min, respectively. Metabolic acidosis (pH 7.00, PaCO2 40 torr) was induced by the iv infusion of 1-M ammonium chloride solution (NH4Cl). In the normal acid-base state, both db-cAMP and dopamine significantly increased cardiac output and decreased systemic vascular resistance (SVR). During metabolic acidosis, db-cAMP increased cardiac output by 69 +/- 14% and decreased SVR by 36 +/- 2%, while dopamine did not produce changes in cardiac output and increased SVR. Dopamine caused an elevation of epinephrine and norepinephrine in the normal acid-base state, but db-cAMP did not. During metabolic acidosis, dopamine significantly increased the plasma concentration of epinephrine and norepinephrine, while db-cAMP significantly decreased epinephrine concentration. These results suggest that db-cAMP may have a more beneficial effect on hemodynamics compared with dopamine when therapeutic support is needed during circulatory insufficiency with severe metabolic acidosis.