Increase in hematocrit, hemoglobin and red cell mass in normal mice after treatment with cyclic AMP (38543).

Chronic treatment of normal mice with either dibutyryl cyclic AMP or erythropoietin produced elevations in the hematocrit, hemoglobin concentration and red cell mass when compared to these same hematological parameters in untreated mice. Dibutyryl cyclic AMP increased red cell mass by 46% while ESF treatment resulted in a 56% increase in red cell mass. These studies confirm earlier reports of the effects of cyclic AMP in increasing radioactive iron incorporation into red cells and further indicate that this change is associated with an absolute increase renal cyclic AMP concentrations probably stimulate erythropoiesis as a consequence of increased kidney production of erythropoietin.     

Effect of cyclic AMP,theophylline and caffeine on the glucose repression of sporulation inSaccharomyces cerevisiae

Summary Repression of the sporulation ability ofSaccharomyces cerevisiae by glucose present in the presporulation medium was studied. Glucose lowered sporulation ability when added to the presporulation medium containing yeast extract but did not do so when added to the presporulation medium without glucose. The glucose-repressed sporulation ability was recovered by the addition of cyclic AMP, and theophylline or caffeine to the presporulation culture. Theophylline promoted the action of cyclic AMP, but caffeine did not. The effect of caffeine to reverse glucose repression was greater than that of cyclic AMP and theophylline.     

Cellular cyclic AMP in dispersed mucosal cells from guinea pig stomach.

In dispersed mucosal cells from guinea pig stomach cyclic AMP was increased 4-fold by theophylline, 5-fold by prostaglandin E2, and 10- to 15-fold by histamine. Theophylline augmented the increase in cellular cyclic AMP caused by histamine or prostaglandin E1 and the actions of histamine and prostaglandin E1 were additive. Cellular cyclic AMP was not altered by carbachol, gastrin, secretin, vasoactive intestinal peptide, glucagon, insulin or the octapeptide of cholecystokinin. Metiamide or diphenhydramine but not atropine inhibited the increase in cellular cyclic AMP caused by histamine, but did not alter the concentration of cyclic AMP in control cells or in cells incubated with theophylline or prostaglandin E1.     

The action of cyclic AMP on GA3 controlled responses VI. Characteristics of the promotion of light-inhibited seed germination in Phacelia tanacetifolia by GA3 and cyclic 3',5'-adenosine monophosphate

GA₃ and cyclic AMP were found to promote the germination (inlight) of light inhibited Phacelia tanacetifolia seed to thelevels obtained with dark controls. The GA₃ and cyclic AMP promotedgermination was inhibited by ABA and cycloheximide but not by6-methyl purine. The hormone and the nucleotide were not requiredfor the entire incubation period to obtain maximum germination. Theophylline and caffeine also promoted germination of theseseeds and 8-bromoadenosine cyclic AMP was found to be a betterpromoter of germination than cyclic AMP. Of a variety of nucleotidestested, only cyclic AMP promoted germination. This study supportsthe hypothesis that cyclic AMP is involved in some manner inGA₃-induced seed germination. (Received January 22, 1974; )     

Hormonal regulation of collagen degradation in the uterus: Inhibition of collagenase expression by progesterone and cyclic AMP

Dibutyryl cyclic AMP markedly increases the ability of progesterone to prevent the expression of collagenase activity in cultures of post-partum rat uterus. Dibutyryl cyclic AMP itself and, to a lesser extent, native cyclic AMP, are capable of producing a partial decrease in enzyme activity, but complete abolition is not observed at high cyclic nucleotide concentrations (5 mM) in the culture medium. Theophylline, when added to cultures, mimics the effect of dibutyryl cyclic AMP. Other cyclic nucleotides were without effect on levels of collagenase activity in the uterine cultures.When non-inhibitory concentrations of either dibutyryl cyclic AMP (1 · 10^?4 M) or theophylline (1 · 10^?4 M) are added to cultures together with a non-inhibitory concentration of either progesterone (5 · 10^?6 M) or the potent progesterone analogue Provera (1 · 10^?8 M) the ability of the tissue to produce collagenase is decreased by 40–70%. Collagenase activity is consistently diminished more than additively by combinations of steroid and cyclic nucleotide. Theophylline mimics the effect of dibutyryl cyclic AMP on steroid activity in culture. In the presence of dibutyryl cyclic AMP, diminution of collagenase activity can be observed at concentrations of steroid more than two orders of magnitude lower than the normal minimally inhibitory dose. Reduction of collagenase activity is reflected in all experiments by a concomitant decrease in the normal proteolytic degradation of collagen in the tissue ex-plants. The possibility that progesterone acts in the uterus to raise cyclic AMP levels is suggested by the fact that uterine tissue, when cultured in the presence of progesterone, contains reduced levels of cyclic nucleotide phosphodiesterase.These data suggest that, in some way a cyclic AMP-mediated system is critically involved in the control of collagenase activity by progesterone in the rat uterus.     

Cyclic AMP and citric acid accumulation by Aspergillus niger

Aspergillus niger accumulated citric acid in the medium under certain conditions. Cyclic AMP concentrations of the order of 10^?6M and higher caused an increase in the rate of citrate synthesis. Adenosine, ATP, and cyclic GMP at 10^?3M also stimulated, but were ineffective at 10^?4M. 5′-AMP had no effect while 5′-GMP and guanosine inhibited slightly. ADP showed a 42% inhibition. Theophylline enhanced the cyclic AMP effect. It is proposed that citric acid accumulation by Aspergillus niger may result from abnormal cyclic AMP metabolism.     

Effects of beta-adrenergic catecholamines on potassium transport in turkey erythrocytes.

Isoproterenol stimulates cellular accumulation of cyclic adenosine 3':5'-monophosphate (cyclic AMP) and produces a 2- to 4-fold increase in bidirectional potassium fluxes in turkey erythrocytes. Ouabain, which does not alter catecholamine-stimulated cellular cyclic AMP, inhibits potassium influx by 50 to 70%, does not alter potassium outflux or isoproterenol-stimulated potassium influx, but increases isoproterenol-stimulated potassium outflux. Stimulation of potassium transport by isoproterenol can be reproduced by adding cyclic AMP to the medium and is inhibited by propranolol or dichloroisoproterenol but not by phentolamine. Theophylline at concentrations which inhibit cyclic nucleotide phosphodiesterase in isolated turkey erythrocyte plasma membranes by greater than 90%, does not augment isoproterenol stimulation of cellular cyclic AMP or of potassium transport but does potentiate stimulation of potassium influx produced by adding cyclic AMP to the medium. Isoproterenol-stimulated cellular cyclic AMP increases steadily for at least 2 hours. Potassium transport, however, increases rapidly, becomes maximal after 20 to 30 min of incubation, and thereafter decreases progressively so that after 2 hours of incubation potassium fluxes are only slightly greater than for the control. Ouabain prolongs the duration of catecholamine-stimulated potassium influx and potassium outflux, reflecting its ability to relieve the refractoriness developed by turkey erythroyctes to endogenous cyclic AMP.     

Evidence that endogenous cyclic AMP does not modulate serum sulfation factor action on embryonic chicken cartilage

The role of cartilage cyclic AMP as a mediator or modulator of serum sulfation factor (SSF) action on embryonic chicken cartilage was assessed. Media with concentrations of rat serum (7.5%) sufficient to maximally stimulate chondromucoprotein synthesis as measured by ³⁵SO₄ incorporation did not change cartilage cyclic AMP levels. Theophylline (2.5mM) doubled cyclic AMP in cartilage incubated in media but had no effect on ³⁵SO₄ incorporation. In media containing 5% rat serum, theophylline at 0.5, 1.5 and 2.5mM caused a similar and significant rise in tissue cyclic AMP but only 2.5mM inhibited SSF stimulated ³⁵SO₄ incorporation. The data indicate that cartilage cyclic AMP neither mediates nor modulates SSF action on cartilage chondromucoprotein synthesis.     

Cyclic AMP is an inhibitor of stalk cell differentiation in Dictyostelium discoideum

Cyclic AMP and DIF-1 (1-(3,5-dichloro-2,6-dihydroxy-4-methoxyphenyl)-1-hexanone) together induce stalk cell differentiation in vitro in Dictyostelium discoideum strain V12M2. The induction can proceed in two stages: in the first, cyclic AMP brings cells to a DIF-responsive state; in the second, DIF-1 alone can induce stalk cell formation. We report here that during the DIF-1-dependent stage, cyclic AMP is a potent inhibitor of stalk cell differentiation. Addition of cyclic AMP at this stage to V12M2 cells appreciably delays, but does not prevent, stalk cell formation. In contrast, stalk cell differentiation in the more common strain NC4 is completely suppressed by the continued presence of cyclic AMP. This fact explains earlier failures to induce stalk cells in vitro in NC4. We now consistently obtain efficient stalk cell induction in NC4 by removing cyclic AMP in the DIF-1-dependent stage. Cyclic AMP also inhibits the production of a stalk-specific protein (ST310) in both NC4 and a V12M2 derivative. Adenosine, a known antagonist of cyclic AMP action, does not relieve this inhibition by cyclic AMP and does not itself promote stalk cell formation. Finally, stalk cell differentiation of NC4 cells at low density appears to require factors in addition to cyclic AMP and DIF-1, but their nature is not yet known. The inhibition of stalk cell differentiation by cyclic AMP may be important in establishing the prestalk/prespore pattern during normal development, and in preventing the maturation of prestalk into stalk cells until culmination.     

Hormonal regulation of amino acid accumulation in human fetal liver explants Effects of dibutyryl cyclic AMP,glucagon and insulin

α-Aminoisobutyrate accumulation by human fetal liver explants in organ culture is stimulated by dibutyryl cyclic AMP ($\text{N}{}^6\text{,}{}^2\text{′O-}\text{dibutyryl}$ adenosine 3′–5′: cyclic monophosphate), glucagon or insulin. Theophylline increased the effect of submaximal concentrations of dibutyryl cyclic AMP or glucagon. Maximal concentrations of glucagon and dibutyryl cyclic AMP yielded the same results as either agent alone. A period of about 4–6 h was required to observe the stimulatory effect of dibutyryl cyclic AMP or insulin, which could be completely prevented by simultaneous incubation with cycloheximide. Maximal effects of either dibutyryl cyclic AMP or glucagon plus insulin produced additive results. These data support the hypothesis that insulin acts via a mechanism independent of the glucagon—cyclic AMP pathway in liver tissue.In addition, the pharmacologic receptor for glucagon was detected in liver explants from a 30-mm (crown - rump) specimen (6 weeks gestation). The liver had the competence to respond to dibutyryl cyclic AMP by the 36-mm stage. Tissue from a 36-mm specimen did not respond to insulin, but a clear response was elicited from a specimen at the 48-mm stage. These data demonstrate the ability of human fetal liver to respond to hormones at a very early stage in gestation.     

Changes in cyclic AMP and cyclic GMP concentrations during the action of 5-hydroxytryptamine on an insect salivary gland.

Salivary glands from adult blowflies (Calliphora erythrocephala Meigen) were studied in vitro. The time course of changes in cyclic AMP content of the glands was followed at different concentration of 5-hydroxytryptamine. There was an immediate biphasic rise and fall in cyclic AMP content, following by a slower rise and subsequent gradual decline. The initial rise preceded the onset of fluid secretion by the glands. Rises in cyclic AMP content were inhibited by compound RMI 12330 A (an adenylate cyclase inhibitor) and were halted after about 15-20s if the glands were deprived of Ca2+. Theophylline (a phosphodiesterase inhibitor) abolished the decline phase of the fast response, Losses of cyclic AMP from the glands either to the bathing medium or to the saliva were small and could not account for the rapid fall found. Evidence is presented that cyclic GMP is not involved in the process of initiating secretion in the blowfly salivary gland.     

Mechanisms of Cyclic AMP Regulation in Cerebral Anoxia and Their Relationship to Glycogenolysis

Abstract: Anoxia elevates levels of cyclic AMP and depresses levels of cyclic GMP in cerebral cortex of mice. Similar effects are also observed in other regions of the brain. Aminophylline inhibits accumulation of cyclic AMP about 50% in hippocampus and cerebellum, but not in cerebral cortex and striaturn; however, this effect requires high doses (²⁵⁰ mgikg). Pretreatment of animals with reserpine, which depletes brain stores of norepinephrine, dopamine, and serotonin, and also produces sedation and mild hypothermia, markedly inhibits accumulation of cyclic AMP in all regions of anoxic brain. Destruction of norepinephrine terminals by treatment of neonatal animals with ⁶-OH- dopamine, which does not sedate or produce hypothermia, has an effect on cyclic AMP levels similar to that of reserpine. None of the above treatments modifies the effect of anoxia on cyclic GMP levels. These data indicate that norepinephrine is a major regulator of cyclic AMP levels in anoxic brain and that adenosine and, perhaps, other unidentified substances have lesser roles in this process. In contrast, biogenic amines and adenosine appear to have no effect on cyclic GMP regulation in anoxic brain. Reserpine slows the activation of phosphorylase and the utilization of ATP, and slightly attenuates the breakdown of glycogen caused by anoxia, but has no effect on the changes in glucose, lactate, or phosphocreatine. In contrast, ⁶-OH-dopamine has no effect on any of these anoxiainduced changes. It is concluded that the effect of reserpine on phosphorylase, glycogen, and ATP is most likely related to the hypothermic and sedative effect of the drug, and that either cyclic AMP is not responsible for initiating glycogenolysis in anoxic brain or only a small rise in cyclic AMP levels is necessary for this process.     

Involvement of cellular cyclic AMP in theophylline-induced sugar accumulation in chicken intestinal epithelial cells

We have studied the possible involvement of cellular cyclic AMP in theophylline-induced sugar gradient enhancement in isolated chicken enterocytes. Theophylline increases 3-O-methylglucose accumulation 3-fold after 30 min incubation. Exogenous cyclic AMP enhances sugar accumulation by 48%. Adenylyl cyclase inhibitor RMI 12 330A reduces theophylline-induced sugar gradients by 22% and theophylline-induced cyclic AMP levels by 24.5%. At the concentration used, RMI 12 330A has no effect on 3-O-methylglucose accumulation or basal cellular cyclic AMP. Since theophylline has a rapid inhibitory effect on Na+-independent sugar permeability, we conclude that the effects of the drug on sugar gradients are the result of its acting by both direct - surface membrane - and indirect - cyclic AMP mediated - mechanisms. The effect of theophylline and exogenous cyclic AMP on sugar accumulation is independent of external chloride.     

Effects of isoproterenol and forskolin on tension, cyclic AMP levels, and cyclic AMP dependent protein kinase activity in bovine coronary artery

The effects of isoproterenol and forskolin on tension, cyclic AMP levels, and cyclic AMP dependent protein kinase activity were compared in helical strips of bovine coronary artery. Elevation of cyclic AMP and activation of the protein kinase appeared to be well correlated with relaxation of potassium-contracted arteries by isoproterenol. Forskolin, at 1 microM or higher concentrations, also markedly elevated cyclic AMP levels, activated the kinase, and relaxed the arteries. However, a lower concentration of forskolin (0.1 microM) caused significant increases in both cyclic AMP levels and cyclic AMP dependent protein kinase activity, but did not relax the muscles. Relaxation caused by isoproterenol was accompanied by an apparent translocation of cyclic AMP dependent protein kinase activity from the soluble to the particulate fraction in these preparations. A similar shift in the distribution of the kinase was caused by various concentrations of forskolin, irrespective of whether the arteries were relaxed or not. In contrast to previous results in other tissues, low concentrations of forskolin (less than or equal to 1 microM), which themselves markedly elevated cyclic AMP levels in the arteries, did not potentiate the effects of isoproterenol on cyclic AMP levels or tension in these preparations. These results suggest that either cyclic AMP is not solely responsible for the relaxation caused by these agents, or some form of functional compartmentalization of cyclic AMP and cyclic AMP dependent protein kinase exists in this tissue.     

The effect of cyclic AMP and prostaglandins on the fibrinolytic activity of mouse neuroblastoma cells.

The C1300 mouse neuroblastoma cell line was found to produce plasminogen activator which is secreted into the growth medium. The intra- and extracellular activities of this enzyme were markedly increased (up to 14 fold) by treatment with cyclic AMP agents. Prostaglandins E₁ and E₂ and butyric acid were the most efficient inducers followed by propionic acid and dibutyryl cyclic AMP. Theophylline was found to be ineffective. The highest enzyme activities were found in cells exposed simultaneously to prostaglandin E₁ and dibutyryl cyclic AMP.     

Induction of glomerulopressin production by cyclic AMP

Isolated rat livers were perfused with gassed Krebs-Ringer-Bicarbonate and different doses of theophylline and dibutyryl cyclic AMP were added to the perfusing solution. The perfusates were ultrafiltrated through Diaflo UM-05 membranes. The glomerulopressin activity of the ultrafiltrates were assayed in the tonic tension contraction (TTC) of isolated stomach fundus from rats. As glomerulopressin is known to be a glucuronide, it was inactivated with beta-glucuronidase to confirm that the effect on the stomach fundus was due to the glomerulopressin and not to another substance. It was observed that doses of theophylline between 2 x 10(-3) M and 2 x 10(-5) M enhanced glomerulopressin production. However, there was no relationship between dose of theophylline and the response, and a dose of theophylline 2 x 10(-6) M has no activity. The perfusion with dibutyryl cyclic AMP at 5 x 10(-8) M increased the amount of glomerulopressin produced by the liver. This was a log-dose response of glomerulopressin production to dibutyryl cyclic AMP between 5 x 10(-8) M and 5 x 10(-4) M. Theophylline (2 x 10(-6) M) potentiated the activity of cyclic AMP (5 x 10(-8) M). These results support the view that cyclic AMP is intracellular mediator of the hepatic production of glomerulopressin.     

Cyclic AMP and the regulation of cholesterol metabolism.

Cyclic AMP has been implicated to a greater or lesser extent in the regulation of four key enzymes which interact to regulate intracellular cholesterol metabolism; HMG CoA reductase; ACAT; cholesteryl ester hydrolase; and cholesterol 7 alpha hydroxylase. The relationship between these enzymes and the sites where current evidence suggests that cyclic AMP may be involved are summarized in Fig. 3. Cholesterol 7 alpha hydroxylase controls the catabolism of cholesterol to bile acids in the liver, and thus its removal from the body via the bile, but does not have a major role in cholesterol metabolism in extrahepatic tissues. It is clear that cyclic AMP is able to influence the activity of this enzyme in liver sub-cellular fractions and isolated hepatocytes in vitro, and studies in our laboratory have shown that changes in Ca2+ fluxes within the cell may be important in its mechanism of action. Whether or not the cyclic nucleotide has a role regulating cholesterol 7 alpha hydroxylase activity in vivo, however, is not known. HMG CoA reductase is inactivated by phosphorylation both in vitro and in vivo, but although cyclic AMP and glucagon have been shown to inhibit the enzyme, cyclic AMP-dependent protein kinase is not directly involved. The exact mechanism by which the cyclic nucleotide influences the system remains unclear, but it may be related to activation of microsomal phosphatases. The activity of ACAT has been shown to be modulated by phosphorylation in a number of tissues in vitro, but the involvement of cyclic AMP has not been unequivocally demonstrated.(ABSTRACT TRUNCATED AT 250 WORDS)     

Serotonin-activated adenylate cyclase and the possible role of cyclic AMP in modulation of buccal muscle contraction in Aplysia

The possible role of cyclic AMP in mediating opposite modulatory effects of serotonin (5-HT) on Aplysia buccal mass muscles E1 and E2 was examined. Serotonin enhances E1 contractions and inhibits E2 contractions. Adenylate cyclase in membranes of both E1 and E2 is stimulated approximately 180% by 10(-6) M 5-HT and 300% by 10(-3) M 5-HT. Dibutyryl cyclic AMP and 8-benzylthio cyclic AMP mimicked the effect of 5-HT on E1 but had no effect on E2. Theophylline (Th) and isobutylmethylxanthine (IBMX) mimicked the effect of 5-HT on E1 at high concentrations. Concentrations of Th and IBMX low enough not to have any direct effect on contraction increased both the magnitude and duration of the effect of 5-HT on E1 contraction. Neither Th nor IBMX had a direct effect on E2 contraction, although Th produced a small increase in the effect of 5-HT on E2. These data are consistent with the hypothesis that cyclic AMP mediates the enhancement effect of 5-HT on E1 contraction. Other mechanisms probably mediate the effect of 5-HT on E2 contraction.     

Modulation by Unsaturated Fatty Acids of Norepinephrine- and Adenosine-Induced Formation of Cyclic AMP in Brain Slices

Abstract: The effect of linoleic acid on the formation of cyclic AMP in the slices of guinea pig cerebral cortex was examined. Treatment of the slices with linoleic acid resulted in an increase of basal and of norepinephrine-stimulated formation of cyclic AMP. The stimulatory effect on the basal level of cyclic AMP was not specific for linoleic acid: the potency of the fatty acid was related to the magnitude of unsaturation. In contrast, the enhancement of norepinephrine-stimulated formation of cyclic AMP seemed relatively specific for linoleic acid and arachidonic acid. Linoleic acid markedly enhanced the stimulated formation of cyclic AMP by histamine and adenosine, as well that by norepinephrine, without affecting that by excitatory amino acids and veratridine. Theophylline, adenosine deaminase, and 2'-deoxyadenosine antagonized the effect of linoleic acid. Linoleic acid enhanced the maximum responses to norepinephrine and adenosine without altering the ED₅₀ values for these agonists. When linoleic acid-treated slices were washed with Krebs-Ringer containing defatted bovine serum albumin, both enhancement of the response to norepinephrine and the amount of [¹⁴C]linoleic acid incorporated in a free form significantly diminished.     

Hyperoxic-induced alterations in lung cell structure and function. Effects on cellular cyclic AMP content and comparison to alterations produced by exogenous cyclic AMP

Hyperoxic exposure in vitro of two lung-derived cell types (the epithelial-derived L2 cells and WI-38 fibroblasts) inhibits cellular replication, produces striking morphologic changes and may result in cell death; these effects have been observed consistently in other cell types. Hyperoxic exposure of L2 cells is associated with an increase in cellular cyclic AMP content (cellular cyclic AMP content 454 +/- 115 fmol/micrograms DNA in cells exposed to pO2 677 Torr for 96 h compared to 136 +/- 17 fmol/microgram DNA in air-grown cells). Hyperoxic exposure of WI-38 fibroblasts is not associated with increased cyclic AMP content. Although cultivation of L2 cells in the presence of exogenous dibutyryl cyclic AMP does inhibit replication and produce morphologic alterations, similar effects are produced by sodium butyrate alone. Hyperoxic exposure alters cyclic AMP metabolism in some cell types, but the structural and functional alterations observed in L2 cells and WI-38 fibroblasts following hyperoxic exposure are not produced by changes in cellular cyclic AMP content.