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At least 19 recordsLinked to original sources
PubMed1976

Cyclic AMP and growth of Ehrlich ascites tumor cells. Lack of cyclic AMP elevation in nutritionally deprived cells and mechanism of retardation of growth by dibutryl cyclic AMP.

Cyclic AMP levels in Ehrlich ascites tumor cells changed little after deprivation of cells of essential nutrients, serum, glucose and amino acids, deprival of each of which leads to marked inhibition of growth and protein synthesis. Cyclic AMP levels also changed little after the addition of these nutrients to deprived cells. Thus cyclic AMP is not likely to be the intracellular mediator for growth regulation by these three nutrients. Elevation of cyclic AMP levels for short periods by exposure of cells to choleratoxin or theophylline produced only slight changes in parameters of protein synthesis (polyribosome pattern and rate of [3H]leucine incorporation). An exposure for 1 day to dibutyryl cyclic AMP did not inhibit cell growth. However, prolonged exposure to dibutyryl cyclic AMP inhibited the multiplication of Ehrlich ascites cells both in suspension and in stationary cultures. No morphological effects were evident in the former; in the latter, cells attached firmly to the substratum and formed elongated cytoplasmic processes. Inhibition of cell multiplication by dibutyryl cyclic AMP was related to cell density and to serum concentration. Cells in dibutyryl cyclic AMP-containing media plated at low cell densities multiplied as rapidly as control cells. The final densities cells reached were determined by the serum concentration; in dibutyryl cyclic AMP-containing media these densities were about one-half those of respective control cells. Limitation of cell multiplication by dibutyryl cyclic AMP was reversed by the addition of serum, by resuspending cells at lower densities, or by resuspending cells in media without dibutyryl cyclic AMP. These findings suggested that dibutyryl cyclic AMP may affect the utilization of serum factors by cells. Dibutyryl cyclic AMP did not inactivate serum factors and did not change the rate at which cells depleted the growth medium of serum factors. Dibutyryl cyclic AMP may limit cell multiplication by increasing the cellular requirement for serum factors.

Amino Acids↗
PubMed1977

The cyclic AMP response to glucagon. Comparison of tissue and plasma cyclic AMP levels in the rabbit.

The effects of glucagon on tissue and plasma cyclic AMP levels have been investigated in rabbits anesthetized with urethane. Glucagon (2 nmole/kg.) caused at least a twofold increase in hepatic cyclic AMP, which reached a peak within two minutes and declined to basal values after 40 minutes. Plasma cyclic AMP also increased at least twofold, reaching a peak at 10 minutes and declining to basal values after 60 minutes. Glucagon (20 nmole/kg.) stimulated hepatic and plasma cyclic AMP in a manner indistinguishable from that observed at the lower dose. Hepatectomy abolished the plasma cyclic AMP responses to glucagon, and no significant stimulation of cyclic AMP concentration was noted in the heart, adipose tissue, small bowel, or kidney. Cyclic AMP hydrolysis was estimated in blood taken before and after administration of glucagon. Glucagon (2 nmole/kg.) increased cyclic AMP hydrolysis slightly, but this was explained by the raised cyclic AMP levels. By contrast, cyclic AMP hydrolysis increased two-to-threefold in blood taken 20 and 40 minutes after glucagon (20 nmole/kg.). The higher dose of glucagon also stimulated cyclic AMP hydrolysis in crude liver homogenate, which could not be explained by increases in cyclic AMP concentration. The increase in cyclic AMP hydrolysis observed in blood and liver may partly explain the failure to show additional stimulation of hepatic and plasma cyclic AMP levels with the higher dose of glucagon. Despite the changes in cyclic AMP hydrolysis, a highly significant correlation was observed in individual rabbits between the hepatic and plasma cyclic AMP responses to glucagon (2 and 20 nmole/kg.), when these were calculated as incremental areas above mean basal levels. It is suggested that measurement of plasma cyclic AMP levels after stimulation by glucagon may be an accurate index of the hepatic cyclic AMP response to glucagon in vivo.

Animals↗
PubMed1975

The role of cyclic AMP in the chemotactic responsiveness and spontaneous motility of rabbit peritoneal neutrophils. The inhibition of neutrophil movement and the elevation of cyclic AMP levels by catecholamines, prostaglandins, theophylline and cholera toxin.

Agents known to affect intracellular levels of cyclic AMP in many diverse systems have been tested for their effect on the chemotaxis induced by Escherichia coli culture filtrates, spontaneous motility and cyclic AMP levels of rabbit peritoneal neutrophils. Prostaglandin E1 and A1 but not prostaglandin F2alpha increased neutrophil cyclic AMP levels and, correspondingly, only the former two prostaglandins inhibited chemotaxis. Nevertheless, a quantitative relationship between prostaglandin stimulation of cyclic AMP and inhibition of chemotaxis could not be found. Epinephrine, isoproterenol, and, to a much lesser extent, norepinephrine increased neutrophil cyclic AMP through beta adrenergic stimulation. Only epinephrine and isoproterenol inhibited chemotaxis, but the inhibition was variable and not related to the ability of these catecholamines to increase intracellular cyclic AMP. Cholera toxin increased neutrophil cyclic AMP after a 30-min lag period which paralled its inhibitory effect on chemotaxis and spontaneous motility. However, the effect on chemotaxis require 50 ng/ml of toxin whereas the effect on cyclic AMP was manifested at 2 ng/ml of toxin. Prior to 30-min preincubation there was no effect of even 1250 ng/ml of toxin on either cyclic AMP or chemotaxis. Choleragenoid prevented the effects of toxin on both cyclic AMP and chemotaxis. The bacterial chemotactic factor obtained from E. coli culture filtrates did not effect a measurable change in levels of neutrophil cyclic AMP. The data indicate that even though cyclic AMP is not, in the main sequence of events, triggering the chemotactic response, increases in neutrophil cyclic AMP may modulate the movement and thus the chemotactic responsiveness of the neutrophil.

Animals↗
PubMed1976

Possible role of cyclic AMP in the relaxation process of mammalian heart: effects of dibutyryl cyclic AMP and theophylline on potassium contractures in cat papillary muscles.

The effect of dibutyryl cyclic AMP (DB-c-AMP; 3 X 10(-4)-3 X 10(-3) M) on electrically induced twitch and high potassium (142.4 mM KCl)-induced contracture tension was studied in papillary muscles from normal and reserpinized cats ([Ca]0 1.8 mM; 25 degrees C; pH 7.4). In both groups of preparations, the increase in twitch tension evoked by DB-c-AMP was accompanied by an abbreviation of the time to peak force and of relaxation time. In the same preparations, the high potassium contracture was markedly depressed by DB-c-AMP in a concentration-dependent manner. Similar results were obtained with the N6-monobutyryl derivative of cyclic AMP. The relaxing effects of the cyclic nucleotides on KCl contractures did not appear to be due to possible non-cyclic breakdown products: adenosine, 5'-AMP and sodium butyrate did not attenuate contracture tension at concentrations up to 3 X 10(-3) M. The same applies to ATP and non-cyclic N6-2'-0-3'-0-tributyryl-adenosine-monophosphate. Theophylline (10(-2) M) was found to prolong the relaxation time of the twitch and to enhance the high KCl contracture. It is concluded that cyclic AMP may be capable of modulating the relaxation process of mammalian heart and that not only the positive inotropic but also the relaxant effects of catecholamines on myocardium described before may be mediated by the cyclic AMP system. The relaxant effects of cyclic AMP derivatives on intact myocardial preparations are attributed to a stimulation by cyclic AMP of the calcium transport of the sarcoplasmic reticulum (SR) and are interpreted to be a corollary to the effects of cyclic AMP previously obtained on isolated SR preparations.

Animals↗
PubMed1977

Effects of cyclic AMP and dibutyryl cyclic AMP on cerebral hemodynamics and metabolism in the baboon.

Adenosine 3',5'-cycle monophosphate (cyclic AMP) (0.5 mg/kg) was infused into the carotid artery of baboons anesthesized with sodium pentobarbital, causing a biphasic increase in cerebral blood flow (CBF) and reduction in cerebrovascular resistance (CVR) associated in each phase with stimulation of cerebral metabolism evidenced by increased cerebral oxygen consumption (COMRO2) and cerebral glucose consumption (CMRG1). Intracarotid dibutyryl cyclic AMP (0.5 mg/kg) caused a monophasic increase in CBF and reduction of CVR but failed to alter cerebral metabolism. This may be due to its rapid removal from the circulation with ineffective passage across the blood-brain barrier since intracisternal infusion of dibutyryl cyclic AMP caused sustained increase in CBF, CMRO2 and CMRG1 and reduction in CVR. Intracarotid AMP (0.4 mg/kg) and adenosine (0.3 mg/kg) caused an immediate and more marked increase in CBF and decrease in CVR unassociated with cerebral metabolic change making it unlikely that the observed effects of cyclic AMP can be attributed to its breakdown products. Cyclic AMP or its dibutyryl derivative may alter cerebral metabolism secondary to neuronal activation but increase in glucose/oxygen utilization ratio after intracarotid cyclic AMP and intracisternal dibutytyl cyclic AMP also suggests an influence on enzymatic regulation of glucose metabolism.

Adenosine↗
PubMed1979

Interaction of rat muscle AMP deaminase with myosin. I. Biochemical study of the interaction of AMP deaminase and myosin in rat muscle.

AMP deaminase was completely solubilized from rat skeletal muscle with 50 mM Tris-HCl buffer (pH 7.0) containing KCl at a concentration of 0.3 M or more. The purified enzyme was found to be bound to rat muscle myosin or actomyosin, but not to F-actin at KCl concentrations of less than 0.3 M. Kinetic analysis indicated that 1 mol of AMP deaminase was bound to 3 mol of myosin and that the dissociation constant (Kd) of this binding was 0.06 micrometer. It was also shown that AMP deaminase from muscle interacted mainly with the light meromyosin portion of the myosin molecule. This finding differs from that of Ashby and coworkers on rabbit muscle AMP deaminase, probably due to a difference in the properties of rat and rabbit muscle AMP deaminase. AMP deaminase isozymes from rat liver, kidney and cardiac muscle did not interact with rat muscle myosin. The physiological significance of this binding of AMP deaminase to myosin is discussed.

AMP Deaminase↗
PubMed1976

Endogenous cyclic AMP in thyroid cell culture. Effect of thyroid-stimulating hormone and dibutyryl cyclic AMP.

We have studied the variations of endogenous cyclic AMP levels in thyroid cells cultured over a period of 7 days in several conditions: in the presence of thyroid-stimulating hormone or dibutyryl cyclic AMP which both promote the aggregation of isolated cells into follicles, and in their absence when cells develop as a typical monolayer. In follicle-forming cells, the cyclic AMP level was found to rise during the first day of culture, then to fall rapidly. In monolayer-forming cells, the cyclic AMP content slightly increases attaining the same level as found in other cells at the fourth day, which remains stable till the seventh day. We have investigated the response of these cells cultured in the presence of dibutyryl cyclic AMP retain the capability of increasing their cyclic AMP concentration whereas monolayer-forming cells do not preserve this quality of thyroid cells.

Animals↗
PubMed1976

CYCLIC AMP/*SECRETl cyclic AMP into push-pull perfusates in freely moving rats.

Cyclic AMP was found in perfusates of push-pull cannula's, chronically placed in the lateral ventricle of freely moving rats. After addition of norepinephrine, dopamine or adenosine to the perfusates the output of cyclic AMP was enhanced, whilst serotonin and histamine were found to be ineffective. The effects of noradrenaline and dopamine on cyclic AMP were found to be mediated by different receptors: haloperidol antagonized only the dopamine response. The effect of norepinephrine was mimicked by isoprenaline, a beta-adrenergic agonist, but was not blocked by propranolol. L-DOPA, given intraperitoneally, increased cyclic AMP levels in the perfusate. We conclude that the release of cyclic AMP into the extracellular medium is a normally occurring phenomenon in brain tissue.

Adenosine↗
PubMed1975

Cyclic AMP, membrane transport and cell division. I. Effects of various chemicals on cyclic AMP levels and rate of transport of neucleosides, hypoxanthine and deoxyglucose in several lines of cultured cells.

Nutrient transport rates and cyclic AMP levels have been implicated in the regulation of cell proliferation. In the present study, however, changes in intracellular cyclic AMP level in several lines of cultured cells (normal 3T3 and SV40 and polyomavirus-transformed 3T3 cells; 3T6, C6 GLIOMA, MOUSE L, and Novikoff rat hepatoma cells) by treatment with papaverine, prostaglandine E1 or isoproterenol did not correlate with the inhibition of the uridine, hypoxanthine or deoxyglucose transport rates by these chemicals. Transport inhibitions by above chemicals or Persantin or Cytochalasin B occurred in most cell lines in the absence of any measurable change in intracellular cyclic AMP concentration. Furthermore, treatment of several cell lines with 1 mM dibutyryl cyclic AMP had no immediate effect on the transport of uridine, thymidine or deoxyglucose, although the transport capacity of the cells for uridine and thymidine, but not that for deoxyglucose, decreased progressively with time of treatment. We also observed that the uridine transport system of all cell lines derived from 3T3 cells and the hypoxanthine transport system of L cells exhibited high degrees of resistance to inhibition by the various chemicals. On the other hand, deoxyglucose transport was inhibited to about the same extent by these chemicals in all the cell lines investigated.

Animals↗
PubMed1975

Adenosine, AMP, cyclic AMP, theophylline and the action and production of erythropoietin.

Erythropoiesis, as measured by the uptake of 59Fe into plethoric mice, is stimulated by adenosine, AMP, cyclic AMP, and dibutyryl cyclic AMP, but not by cytidine, its nucleotides or cyclic GMP. This stimulation is erythropoietin dependent, because it is prevented by anti-erythropoietin. Theophylline neither stimulates erythropoiesis nor potentiates the action of erythropoietin on bone marrow cells in plethoric mice. Theophylline does potentiate the production of erythropoietin in rats following a frief hypoxic exposure but does not cause a similar increase in mice.

Adenine Nucleotides↗
PubMed1977

[Further developments of the AMP-system. A report on the 2nd AMP-symposium and training seminar (author's transl)].

This is a report of a symposium and training seminar of the "Arbeitsgemeinschaft für Methodik und Dokumentation in der Psychiatrie" (AMP). Video-recordings of two psychiatric interviews were shown during the seminar and rated by the participants using the AMP-3-Scale (Psychopathology). Aim of the seminar was a rater training and the preparation of an expert standard rating. These videotapes with the corresponding standard ratings will enable the different clinics using the AMP-System to compare their rating behaviour. The process of achieving an expert standard rating is described. The training seminar was followed by a symposium during which a series of lectures was presented on "Standardized Assessment in Psychiatry", The different working groups of the Association reported about their work and future prospects of the Association were discussed.

Congresses as Topic↗
PubMed1977

Effects of cyclic AMP and dibutyryl cyclic AMP on amino acid transport in the isolated rat ovary.

Prepubertal rat ovaries were incubated in medium containing the non-utilizable amino acids alpha-aminoisobutyric acid (AIB-14C) or 1-aminocyclo-pentane-carboxylic acid (cycloleucine-14C). The rate of uptake of the two amino acids was studied in the isolated ovaries after different incubation periods. Addition of 5mM cyclic AMP (cAMP) caused a slight stimulation of the AIB-transport but in higher concentrations (10-25 mM) an inhibition was noted. With dibutyrl cyclic AMP (dbcAMP) a dose-dependent increase was seen with 0.5-5 mM concentrations with no further effect of higher concentrations. Time course studies were performed with both AIB and cycloleucine in presence of 10 mM dbcAMP and increased uptake values were noted at each time studied (30-240 min). The phosphodiesterase inhibitor aminophyline in lower concentrations did not influence AIB-transport but 5-10 mM caused increased uptake values in the ovaries. The stimulatory action of dbcAMP on amino acid transport was augmented by a low concentration of aminophylline (0.5 mM). Experiments were in addition carried out in the presence of puromycin and under these circumstances it was still possible to enhance amino acid transport by addition of dbcAMP. The results are discussed in relation to earlier reported effects of gonadotropins on ovarian amino acid transport.

Amino Acids↗
PubMed1976

Enzymatic radioiodination of succinyl cyclic AMP tyrosine methyl ester by lactoperoxidase and radioimmunoassay for cyclic AMP.

A highly specific and simple radioimmunoassay for cyclic AMP with a sensitivity of 0.04 picomoles/tube has been developed according to the method of Steiner et al., using 125I-succinyl cyclic AMP tyrosine methyl ester as a tracer. The tracer with higher immunoactivities could be simply and constantly prepared by an enzymatic iodination procedure utilizing lactoperoxidase, radioactive iodide and hydrogen peroxide generated by glucose-glucose oxidase system, rather than by chloramine-T procedure.

Adipose Tissue↗
PubMed1977

Cyclic AMP in action of antidiuretic hormone: effects of exogenous cyclic AMP and its new analogue.

Exogenous cyclic 3',5'-adenosine monophosphate (cAMP) stimulates the effect of the antidiuretic hormone, vasopressin (VP), only in pharmacologic quantities and results have often been inconsistent. The present study examined the ability of a new analogue, 8-[p-Cl-phenylthio]cyclic 3',5'-adenosine monophosphate (C1-PheS-cAMP) to mimic the effect of VP, both biochemically (protein kinase activation) and functionally (hydrosomatic response of perfused collecting tubules) in mammalian kidney tissue. C1PheS-cAMP was found to be about 100 times as effective as cAMP both biochemically and functionally. The increased effectiveness of C1PheS-cAMP is probably is probably due to a greater permeability across the cell membrane and to the resistance of C1PheS-cAMP to enzymatic degradation, Cyclic AMP phosphodiesterase inhibition was observed with C1PheS-cAMP, but its contribution to overall effect was minor. C1PheS-cAMP was found to be more effective than exogenous vasopressin, an effect probably due primarily to its resistance to catabolism. The results provide further new evidence that cAMP and protein kinase are involved in the cellular action of vasopressin. C1PheS-cAMP proved to be a useful tool in the study of hormone action, especially in steps subsequent to cAMP generation.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1975

Direct effects of cyclic AMP and dibutyryl cyclic AMP on renal blood flow.

The direct effects of adenosine 3',5'-cyclic monophosphate (cAMP) and dibutyryl adenosine 3',5'-cyclic monophosphate (D-cAMP) on renal blood flow were studied in dogs under renal perfusion with constant pressure. Cyclic AMP caused a marked phasic decrease in renal blood flow in doses more than 1 mg, while D-cAMP produced a slight increase in that in doses more than 10 mg. The vasoconstrictive effect of cAMP was not blocked by the pretreatment with phenoxybenzamine, but was markedly depressed during the infusion of aminophylline. On the other hand, the vasodilative effect of D-cAMP was not affected either by the pretreatment with propranolol or during the infusion of aminophylline. These findings indicate that cAMP and D-cAMP have an opposite direct effect on the renal artery, independently of the adrenergic receptors. However, there may be a possibility that cAMP produces its vasoconstrictive effect on the renal artery partly through the action of its metabolites.

Aminophylline↗
PubMed1979

Role of calcium dependent regulator protein (CDR) in inhibition of 3',5'-c AMP-phosphodiesterase by influenza virus. I. Isolation and purification of CDR and CDR-dependent 3',5'-c' AMP-phosphodiesterase from chick embryos.

Calcium-dependent regulator protein (CDR) and CDR-dependent 3',5'-c AMP-phosphodiesterase were isolated and partially purified from 12-day chick embryos. Some basic properties of the preparations obtained were described. Native (infectious) but not noninfectious (heat-inactivated) influenza virus in the presence of CDR and ATP reduced the activity of CDR-dependent phosphodiesterase.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1976

Sequential alterations in the hepatic content and metabolism of cyclic AMP and cyclic GMP induced by DL-ethionine: evidence for malignant transformation of liver with a sustained increase in cyclic AMP.

There is evidence than adenosine 3',5'-monophosphate (cAMP) and guanosine 3',5'-monophosphate (cGMP) may have antagonistic actions on cell growth, with cAMP inhibiting and cGMP stimulating this process. However, reductions in cAMP and increases in cGMP are not charactersitic of all neoplastic tissues. Thus, benign and malignant tissues from hepatoma-bearing rats exposed to the hepatic carcinogen DL-ethionine have elevated rather than depressed cAMP, compared to control liver, and parenteral administration of this drug increases hepatic cAMP within hours. In the present study, the effects of ethionine ingestion on the hepatic content and metabolism of both cAMP and cGMP were examined sequentially in rats at 2 and then 6 wk intervals, from the initiation of drug administration until the development of hepatomas. After 2 wk, cAMP content of quick-frozen liver from rats receiving ethionine (E) was significantly increased (826 +/- 91 pmole/g wet weight) above that of liver from pair-fed controls (C, 415 +/- 44), whether calculated by tissue wet weight, protein, or DNA content. In benign tissue from E, higher cAMP was still evident after in vitro incubations of slices with 2 mM 1-methyl-3-iso-butylxanthine (MIX) and was associated with enhanced adenylate cyclase and unchanged high or low Km cAMP-phosphodiesterase activities. These findings are compatible with accelerated cAMP generation in liver from E. Protein kinase activity ratios were significantly increased in frozen liver from E (0.52 +/- 0.04 versus 0.36 +/- 0.03 in C), and the percent glycogen synthetase in the I form was clearly reduced (19% +/- 2% in E versus 47% +/- 5% in c). incubation of hepatic slices from E or C with MIX and/or 10 muM glucagon further increased cAMP and protein kinase activity ratios, data which imply higher effective, as well as total, cellular cAMP in E. Changes in cAMP metabolism and action observed at 2 wk persisted throughout the 38-wk period of drug ingestion. Adenylate cyclase activity, cAMP content, and protein kinase activity ratios of ethionine-induced hepatomas exceeded those of both the surrounding liver from tumor-bearing rats and that of control liver, but alterations in these parameters were qualitatively similar in both tissues from E. By contrast, while cGMP in quick-frozen surrounding liver from tumor-bearing rats (36 +/- 4 pmole/g wet weight) did not differ from that of control liver (30 +/- 3), cGMP in the hepatomas was increased. This change was evident in both frozen tumor (89 +/- 10) and in tumor slices incubated in vitro with MIX (C, 90 +/- 11; surrounding liver, 85 +/- 10; hepatoma 231 +/- 29). These results indicate that malignant conversion can occur in liver with a sustained elevation of both total and effective cAMP during the premalignant phase. The increase in cGMP detected in ethionine-induced hepatomas could also be a key determinant of malignant transformation in the model, although premalignant changes in cGMP were not apparent.

3',5'-Cyclic-AMP Phosphodiesterases↗