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At least 19 recordsLinked to original sources
PubMed1974

Fatty acid degradation in Escherichia coli: requirement of cyclic adenosine monophosphate and cyclic adenosine monophosphate receptor protein for enzyme synthesis.

The strong repression of inducible synthesis of the enzymes of fatty acid degradation by glucose can be partially relieved by the addition of cyclic adenosine 3',5' monophosphate (cyclic AMP) to the growth medium. This reversal of the glucose effect by cyclic AMP is not observed in a mutant (K29) that is unable to grow on fatty acids as sole carbon source and that was found to synthesize low levels of several enzymes specified by the fad regulon. In a revertant selected for the ability to grow on oleate these effects are concomitantly relieved. By both genetic (co-transduction of the mutation with the strA locus) and biochemical experiments (an extract of the mutant strain does not show the cyclic AMP-dependent stimulation of the deoxyribonucleic acid-directed in vitro synthesis of the enzymes of the gal operon), it is demonstrated that the mutant lacks functional cyclic AMP receptor protein (CR protein). It is concluded that, like many other inducible enzyme systems, expression of the enzymes of the fad system requires cyclic AMP and the CR protein.

Acyltransferases↗
PubMed1984

Age associated changes in intracellular cyclic adenosine monophosphate.

Cyclic adenosine monophosphate (cAMP) levels of isolated human peripheral blood lymphocytes show age associated changes. These changes are apparent in basal cAMP levels as well as in cAMP levels after trypsin treatment. Both cord blood lymphocytes and lymphocytes isolated from the blood of old people exhibit lower basal levels of cAMP and diminished increase in cAMP by trypsin treatment, in comparison to lymphocytes isolated from the other age groups. The results seem to indicate a low number of reactive cells and a low reactivity of the cells in the case of cord blood lymphocytes, and a decrease in number of the reactive cells without a decrease in specific reactivity of isolated lymphocytes of old people.

Adolescent↗
PubMed1992

Theophylline and prostaglandin E2 on duodenal bicarbonate secretion: role for 5'-cyclic adenosine monophosphate.

Cyclic adenosine monophosphate (cAMP) has been implicated as an intracellular "second" messenger in duodenal mucosal bicarbonate secretion in animals. The purpose of this study was to determine whether cAMP may mediate duodenal mucosal bicarbonate secretion in humans. In healthy volunteers, a 4-cm segment of proximal duodenum was isolated from gastric and pancreaticobiliary secretions. Either the phosphodiesterase inhibitor theophylline, prostaglandin (PG) E2, or a combination thereof was administered topically to the isolated duodenal mucosa. Theophylline (10(-2) mol/L) and PGE2 (10(-5)-10(-4) mol/L) each significantly increased bicarbonate secretion and transmucosal potential difference. Moreover, when theophylline and PGE2 were administered in combination, the duodenal bicarbonate output was additive compared to either agent alone. When theophylline was infused with increasing doses of PGE2, the dose-response curve was shifted to the left. Furthermore, increases in bicarbonate secretion and transmucosal potential difference were correlated significantly. These results suggest that cAMP may act as an intracellular mediator of human duodenal mucosal bicarbonate secretion.

Adult↗
PubMed1996

Regulation of somatostatin gene transcription by cyclic adenosine monophosphate.

Cyclic adenosine monophosphate (cAMP) stimulates transcription of somatostatin and other target genes with burst-attenuation kinetics. The kinetics of protein kinase (PK-A)-dependent cAMP response element binding protein (CREB) phosphorylation closely parallel the changes in transcription of cAMP-responsive genes by run-on assay. Nuclear translocation of PK-A, visualized by microinjection of fluorescently labeled PK-A holoenzyme, appears to represent the rate-limiting step in CREB phosphorylation and transcriptional activation. We and others have recently characterized a CREB-binding protein (CBP), which specifically recognizes sequences within the Ser133 phosphorylated form of CREB. CBP does not regulate the DNA binding, dimerization, or nuclear targeting properties of CREB, but binds selectively to the kinase-inducible 60 amino acid trans-activation domain (KID) of CREB, critical for PK-A-inducible transcription. We developed an antiserum directed against amino acid 634-648 within the CREB-binding domain of CBP. We detected a 265-kd polypeptide by Western blot as predicted from the cDNA, which coincided with the predominant phospho-CREB-binding activity in Hela nuclear extracts by "Far Western" blot assay. An identical phospho-CREB-binding activity was also found in NIH-3T3 cells. This phospho-CREB-binding protein appeared to be specific for Ser133-phosphorylated CREB, because no such band was detected with CREB labeled to the same specific activity at a nonregulatory phosphoacceptor site (Ser156) by casein kinase II (CKII). Following microinjection into nuclei of NIH-3T3 cells, a cAMP response element (CRE)-lacZ reporter was markedly induced by treatment with 8-Br cAMP plus isobutyl methyl xanthine (IBMX). Coinjection of CBP antiserum with the CRE-lacZ plasmid inhibited cAMP-dependent activity in a dose-dependent manner, but control immunoglobulin G (lgG) had no effect on this response. We can now begin reconstituting PK-A-dependent transcription in vitro, using well-characterized proteins such as CREB, TAF 110, and CBP. The assembly of such factors on cAMP-regulated promoters like somatostain may enable responsiveness to a variety of hormonal stimuli that employ cAMP as their second messenger.

3T3 Cells↗
PubMed1997

Serum uncouples elevation of cyclic adenosine monophosphate concentration from cyclic adenosine monophosphate dependent morphological changes exhibited by cultured pituicytes.

Cultured pituicytes (neurohypophysial astrocytes) are normally flat amorphous cells when incubated (90 min) in a HEPES balanced salt solution (HBSS) but become stellate when incubated in HBSS supplemented with forskolin. This stellation process is attenuated by serum (0.5% vol/vol). The experiments described here were designed to determine whether serum attenuates stellation by modulation of the intracellular cyclic adenosine monophosphate (cAMP) concentration or some other mechanism. It was observed that the effect of serum on forskolin-induced stellation was not affected by pertussis toxin (100 ng/ml) and that serum also inhibited stellation induced by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX; 100 microM). Further, serum inhibited stellation induced by the membrane permeable cAMP analog 8-bromo cAMP (150 microM). These results indicate that although an increase of intracellular cAMP concentration is necessary for pituicyte stellation, an increase of intracellular cAMP concentration may be decoupled from stellation.

Animals↗
PubMed2002

Implication of guanosine 3',5'-cyclic monophosphate, adenosine 3',5'-cyclic monophosphate, adenosine 5'-mono-, di- and triphosphate and fructose-2,6-bisphosphate in the regulation of the glycolytic pathway in hypoxic/anoxic mussel, Mytilus galloprovincialis.

The change in the content of cyclic GMP, cyclic AMP, ATP, ADP, AMP and fructose-2,6-bisphosphate that occurred in the mantle of the mussel Mytilus galloprovincialis Lmk when specimens of this mollusk were subjected to a hypoxia/anoxia situation were assessed. After the early 24 h in anaerobiosis, a clear decrease was observed in the ATP content, which remained close to that value for the rest of the time. AMP content doubled during the early 24 h in anaerobiosis and, from that time on, it remained close to that value. Fructose-2,6-bisphoshate and cyclic GMP showed a similar behavior. The levels of these compounds rose significantly during the early hours in anaerobiosis, and then fell to values similar to those of aerobiosis, remaining constant for the rest of the time. Neither ADP nor cAMP showed significant variations.

Adenosine Diphosphate↗
PubMed1975

Opposing regulatory influences of cyclic guanosine monophosphate and cyclic adenosine monophosphate in the control of cardiac muscle contraction.

The effects of acetylcholine chloride (ACh) and isoproterenol (Iso) on myocardial levels of guanosine 3', 5'-monophosphate (cyclic GMP) and adenosine 3', 5'-monophosphate (cyclic AMP) and on force of contraction were studied in elelctrically driven isolated rabbit atria. Incubation of atria with Tyrode's solution containing ACh (5 x 10(-7) M) produced significant decreases in contractile force that were associated with significant elevations in atrial cyclic GMP levels. Atrial levels of cyclic AMP were significantly lowered at 15 sec after the addition of ACh but were only slightly lowered at earlier time intervals. The effects of acetylcholine on force of contraction and on cyclic nucleotide levels were prevented with atropine (1 x 10(-7) M). The addition of Iso (1 x 10(-7)-M) to isolated atria produced significant increases in contractile force that were associated with significant elevations in effects of Iso on force of contraction and on cyclic nucleotide levels were prevented with practolol (1 x 10(-5) M). The increases in atrial cyclic GMP and cyclic AMP levels following addition of ACh and Iso, respectively, precede the changes in contractile force. These data support our hypothesis that cyclic AMP and cyclic GMP exert oppositional effects on cardiac contrctility.

Acetylcholine↗
PubMed1972

Regulation of adenosine 3',5'-cyclic monophosphate phosphodiesterase activity in fibroblasts by intracellular concentrations of cyclic adenosine monophosphate (3T3-dibutyryl cyclic AMP-SV40-transformed cells-michaelis constants-L cells-prostaglandin E 1 ).

Cyclic AMP-phosphodiesterase is present in various mouse fibroblasts. Contact-inhibited 3T3 cells contain two forms of the enzyme, one with a K(m) of 2.5 muM and the second with a K(m) of 71 muM. As 3T3 cells grow to confluency and cAMP concentrations rise, the activity of the first enzyme increases, whereas that of the second is unchanged. A line of SV40-transformed 3T3 cells with low cAMP concentration also has low levels of the cAMP-phosphodiesterase with a K(m) of 2.5 muM. Treatment of 3T3 and SV40-transformed 3T3 cells with dibutyryl cAMP and theophylline increases cAMP-phosphodiesterase accumulation. This accumulation is blocked by cycloheximide and actinomycin D. The newly formed enzyme resembles the higher affinity enzyme present in unstimulated cells, since it has a K(m) of 1.2-2.0 muM, and is stimulated by snake venom. In L cells in which cAMP concentrations are elevated by treatment with prostaglandin E(1), cAMP phosphodiesterase also accumulates. We conclude that intracellular concentrations of cAMP regulate the synthesis of cAMP-phosphodiesterase, and that cAMP functions as an inducer of the enzyme.

Animals↗
PubMed1976

Effect of angiotensin II on cyclic guanosine monophosphate and cyclic adenosine monophosphate in human plasma.

Infusion of alpha-adrenergic catecholamines increases plasma cyclic guanosine monophosphate (pcGMP), raising the possibility that the pressor effect of these agents may be mediated by cyclic GMP. We infused pressor doses of angiotensin II in 10 studies in 8 normal subject and measured pcGMP and plasma cyclic adenosine monophosphate (pcAMP) by radioimmunoassay. After 120 minutes of infusion, mean pcGMP was 128 +/- 31% (SE) higher than baseline values (P less than 0.01) while pcAMP was increased 30 +/- 10% (P less than 0.05).

Angiotensin II↗
PubMed1996

Hydrolysis of cyclic guanosine monophosphate and cyclic adenosine monophosphate by the penis and aorta of the diabetic rat.

OBJECTIVE: To investigate the hydrolysis of adenosine 3'5'-cyclic monophosphate (cAMP) and guanosine 3'5'-cyclic monophosphate (cGMP) by specific phosphodies-terases (PDEs) in the penis and aorta of diabetic rats. MATERIALS AND METHODS: Non-ketonuric diabetes mellitus was induced in 10 Sprague-Dawley rats with streptozotocin. After 2 months, the rats were killed and their penises and aortae excised. The tissues were incubated with [3H]-cAMP and [3H]-cGMP and the degree of hydrolysis was assessed by separating [3H]-cAMP and [3H]-cGMP from [3H]-AMP and [3H]-GMP, respectively, in the incubation supernatants using thin layer chromatography (polyethyleneimine cellulose developed in 50 mmol/L KCl). RESULTS: The hydrolysis of cAMP and cGMP was significantly reduced in penile and aortic tissue from diabetic rats compared to that of seven age-matched controls. CONCLUSIONS: Such a reduction of PDE activity would result in increased intracellular cyclic nucleotide levels (and thus corporeal smooth muscle relaxation and erection). Consequently, the altered activity of PDE enzyme systems is not related aetiologically to the pathogenesis of diabetic erectile dysfunction. Furthermore, these data consolidate the concept that enhanced cyclic nucleotide synthesis and decreased degradation constitute an adaptive response to counteract the deleterious effects of diabetes mellitus on erectogenic mechanisms. The pathophysiology and therapeutic implications of these findings warrant further investigation.

Animals↗
PubMed1987

Effects of atrial natriuretic factor on cyclic guanosine monophosphate and cyclic adenosine monophosphate accumulation in microdissected nephron segments from rats.

Atrial natriuretic factor (ANF) (1 microM) markedly increased cyclic guanosine monophosphate (cGMP) content in microdissected glomeruli (35-fold) and in microdissected inner medullary collecting ducts (IMCD) (20-fold). ANF caused little or no increase in cGMP content in other nephron segments. The threshold concentration for increased cGMP accumulation by ANF was 0.1-1 nM in IMCD, which is in the range reported for rat plasma. Sodium nitroprusside (1 mM), which selectively stimulates soluble guanylate cyclase, increased cGMP content in glomeruli but not in IMCD. ANF did not alter cAMP accumulation in the absence or presence of vasopressin (AVP) or parathyroid hormone (PTH) in outer and inner medullary tubule suspensions, or in microdissected proximal convoluted tubules (PCT), medullary thick ascending limbs (MAL) or IMCD. These data are compatible with the hypothesis that cGMP is a second messenger for a physiologic action of ANF in the inner medullary collecting duct. ANF apparently activates membrane-bound guanylate cyclase in this segment.

Animals↗
PubMed1997

Orthovanadate stimulates cyclic guanosine monophosphate-inhibited cyclic adenosine monophosphate phosphodiesterase activity in isolated rat fat pads through activation of particulate myelin basic protein kinase by protein tyrosine kinase.

Involvement of protein kinases in the stimulation of cGMP-inhibited cAMP phosphodiesterase (PDE) activity by orthovanadate (vanadate) was studied. When the fat pads were incubated with 2 mM vanadate or 10 nM insulin, the stimulation of myelin basic protein kinase (MBPK) activity in the particulate by vanadate reached a maximum at 60 min. In contrast, insulin showed a transient increase at 20 min. A 60-min incubation of the fat pads with vanadate stimulated all activities of protein tyrosine kinase (PTK), MBPK, and PDE in the particulate, in a similar dose-dependent manner. Amiloride, a PTK inhibitor, inhibited the stimulations of three enzymes by vanadate in a similar concentration range. Enzyme fractions, which were separated from the solubilized particulate, were subjected to the immunoblot analysis. A fraction of MBPK was identified to contain a major protein of mol wt (44K) and a minor one (42K), both of which are immunoreactive with a mitogen-activated protein kinase (MAPK) antibody. The partially purified PDE activity was stimulated by the addition of the partially purified MBPK. The further stimulation was observed with the PTK-activated MBPK. These results suggest that vanadate stimulates in part the PDE activity through the activation of the particulate MBPK, probably MAPKs, by PTK sensitive to vanadate.

3',5'-Cyclic-AMP Phosphodiesterases↗