Turnover of adenosine 3'':5''-cyclic monophosphate in chicken erythrocytes.

Turnover of cyclic AMP was studied in intact chicken erythrocytes. Production of cyclic AMP was stimulated by adrenaline and then blocked by propranolol. The decline in the cyclic AMP concentration under these conditions is solely due to its intracellular degradation, whereas efflux of the nucleotide, although existing in these cells, does not contribute significantly to the change in its concentration. Intracellular degradation of cyclic AMP follows a first-order kinetics with a half-life of about 6 min. Similar half-lives were obtained at widely different adrenaline concentrations or when the ration of propranolol to adrenaline was varied by 25-fold. Theoretical equations were applied to calculate the rates of cyclic AMP synthesis and degradation in the intact cells under different experimental conditions. Maximal adrenaline concentrations raise the rate of cyclic AMP synthesis and its steady-state concentration by about 10-fold. The addition of caffeine causes a further 33% increase in intracellular concentration of the nucleotide, which is in good agreement with the theoretical increase computed from its slowed-down degradation.     

Effect of exercise on plasma cyclic AMP

The purpose of this study was to confirm the relationship between cyclic AMP(cAMP) level in plasma and changes of hormones concentrations in blood, during and after physical exercise. The results were as follows: At rest, plasma cAMP were 23.1 p mole/ml on the average and decreased after glucose loading. The level in plasma increased in proportion to the intensity of exercises. Under the 50% condition of the maximal intensity, cAMP level in plasma was about 40 p mole/ml and the contents of both thyroxine and growth hormone in serum clearly increased. And, under the 70% of the maximal, the contents of both adrenaline and noradrenaline in serum as well as that of cAMP in plasma increased. Plasma cAMP level also increased by prolongation of exercise (ca 45 p mole/ml). And when exercise lasted over 1.5 hrs, plasma glucagon level began to rise. The effect of carbohydrate load to lower the levels of plasma cAMP were also found during physical exercise. These results suggested that the cAMP level in plasma was affected, not only by the some regulating factors of glycolytic activities such as adrenaline and glucagon, but also by the production of thyroxine and growth hormone at the onset of exercise.     

急性低氧对大鼠血液中儿茶酚胺及血小板聚集性的影响

健康ＳＤ雄性大鼠,体重２５０－３００ｇ,麻醉、气管插管,用人工呼吸机经气袋供气,自发吸入氧浓度为９％的氧氮混合气,用高效液相色谱－电化学联合检测法及电阻法检测循环血液中儿茶酚胺及全血血小权聚集性的动态变化。结果：急性低氧１５ｍｉｎ时血液中肾肾上腺素（Ａ）浓度及全血血小板聚集性显著增加（Ｐ〈０．０１）,而去甲肾上腺素（ＮＡ）浓度虽有所增加,但无统计学意义（Ｐ〉０．０５）;复氧１５ｍｉｎ时血液中儿茶酚     

Urinary and plasma cyclic AMP levels during short term starvation in obese man: response to glucagon stimulation.

Glucagon is known to elevate the intracellular concentration of cyclic AMP in the hepatocyte. The increase in intracellular cyclic AMP is reflected by an increase in the plasma concentration of the nucleotide. Intravenous glucagon stimulation was performed on six obese non-diabetic human subjects before and after a three day fast. All patients responded to starvation by a lowering of plasma immunoreactive insulin and blood glucose. Whereas the plasma immunoreactive glucagon concentration increased over the three day period, the plasma and urinary cyclic AMP did not significantly change. Intravenous glucagon promoted qualitatively similar increases in the blood glucose and plasma concentrations of insulin and cyclic AMP before and after three days starvation.     

Anaphylaxis and plasma catecholamines

The concentrations of plasma catecholamines, cyclic AMP glucose, lactate and glycerol were measured in a high IgE-producing strain of Hooded-Lister rats. Immobilization caused an increase in the levels of plasma catecholamines, especially adrenalin. In rats immunized against egg albumin the rise was higher than in non-sensitized controls, possibly indicating a relationship between sympatho-adrenal activity and serum IgE levels. Anaphylaxis caused by egg albumin induced a rapid and huge increase of plasma catecholamines especially adrenaline. The increase of plasma catecholamines was more rapid and pronounced in awake than in anesthetized rats. The plasma levels of adrenaline following anaphylaxis were larger than those obtained following administration of 5 μg adrenaline i.v. Plasma cyclic AMP, glucose and lactate levels were markedly enhanced already before the injection of antigen. On the other hand, glycerol levels were initially low but increased in parallel to the rise in plasma catecholamines. Administration of dextran to Sprague-Dawley rats induced an anaphylactoid reaction and high plasma levels of adrenaline and noradrenaline. The results indicate a massive sympatho-adrenal activation in anaphylactic and anaphylactoid shock and the use of exogenous adrenaline may cause little additional activation of adrenoceptors.     

Hormonal Neuroendocrine and Vasoconstrictor Peptide Responses of Ball Game and Cyclic Sport Elite Athletes by Treadmill Test

ObjectiveOur objective was to evaluate complex hormonal response in ball game and cyclic sport elite athletes through an incremental treadmill test, since, so far, variables in experimental procedures have often hampered comparisons of data.MethodsWe determined anthropometric data, heart rate, maximal oxygen uptake, workload, plasma levels of lactate, adrenaline, noradrenaline, dopamine, cortisol, angiontensinogen and endothelin in control (n = 6), soccer (n = 8), handball (n = 12), kayaking (n = 9) and triathlon (n = 9) groups based on a Bruce protocol through a maximal exercise type of spiroergometric test.ResultsWe obtained significant increases for adrenaline, 2.9- and 3.9-fold by comparing the normalized means for soccer players and kayakers and soccer players and triathletes after/before test, respectively. For noradrenaline, we observed an even stronger, three-time significant difference between each type of ball game and cyclic sport activity.ConclusionsExercise related adrenaline and noradrenaline changes were more pronounced than dopamine plasma level changes and revealed an opportunity to differentiate cyclic and ball game activities and control group upon these parameters. Normalization of concentration ratios of the monitored compounds by the corresponding maximal oxygen uptake reflected better the differences in the response level of adrenaline, noradrenaline, dopamine and cortisol.     

Influence of Naloxone on the cellular immune response to head-up tilt in humans

To evaluate a possible role for β-endorphin in the stress-induced modulation of natural killer (NK) cells, immunologically competent blood cells were followed in eight male volunteers administered either Naloxone or saline (control) during head-up tilt maintained until the appearance of presyncopal symptoms (PS). The PS appeared more rapidly with Naloxone compared to control [5.7 (SEM 1.1) vs 22.3 (SEM 5.1) min; P = 0.01]. The NK cell activity increased threefold during PS partly due to an increase in CD16⁺ and CD56⁺ NK cells in blood. In support, NK cell activity boosted with interferon-α and interleukin 2 rose in parallel with unboosted NK cell activity and NK cell concentration and activities returned to the baseline level after 105 min. The total lymphocyte count and the concentrations of CD3⁺, CD4⁺, CD8⁺, CD16⁺, and CD56⁺ cells increased during PS. Head-up tilt also induced an increase in plasma adrenaline concentration during control PS and a rise in plasma cortisol and adrenocorticotropic hormone concentrations up to 30 min thereafter, whereas no significant changes were found in plasma concentrations of noradrenaline, growth hormone, or β-endorphin. The results would indicate an influence of endorphin on the increase in plasma adrenaline concentration during head-up tilt and at the same time contra-indicate a significant role for adrenaline in the provocation of PS. The influence of head-up tilt on plasma β-endorphin was too small to influence the modulation of the cellular immune system. Accepted: 22 May 1997     

IN VIVO CHANGES OF CEREBRAL CYCLIC ADENOSINE 3'',5''-MONOPHOSPHATE INDUCED BY BIOGENIC AMINES: ASSOCIATION WITH PHOSPHORYLASE ACTIVATION

—The intravenous injection of adrenaline, isoprenaline and histamine to 4-6-day-old chicks resulted in a rapid increase in the cyclic AMP content of cerebral hemispheres that had been removed and frozen within 0·5 s using a freeze-blowing technique. Noradrenaline, dopamine, adenosine, 5-HT and acetylcholine did not significantly alter the nucleotide concentration in vivo. Addition of adrenaline, isoprenaline and histamine to incubated chick cerebral cortex slices also increased the cyclic AMP content of the tissue. Noradrenaline was considerably less potent than these amines and adenosine was ineffective. Low phosphorylase a levels (16 per cent of total activity) were observed in instantaneously frozen cerebral hemispheres of untreated chicks. The injection of adrenaline, isoprenaline and histamine resulted in a rapid conversion of phosphorylase b to a and a significant fall in tissue glycogen. Administration of noradrenaline was without effect on the relative forms of phosphorylase and also failed to influence cerebral glycogen. Phosphorylase activation was not observed in chick cerebral slices under conditions producing large increases in cyclic AMP. It is suggested that in vivo phosphorylase activation and subsequent glycogenolysis may occur, at least in part, in glia and that these cells may be damaged during preparation of cerebral slices. The results provide evidence of a metabolic role for cyclic AMP in cerebral tissue.     

Modulation of peripheral blood mononuclear cell cyclic adenosine monophosphate levels by human very low density lipoprotein

Normal human plasma very low density lipoprotein (VLDL) can inhibit mitogen-induced lymphocyte DNA synthesis. Since early events in lymphocyte activation (e.g., cyclic nucleotide metabolism) are thought to influence the magnitude of later events (e.g., [³H]thymidine uptake) we designed the current studies to compare the effects of VLDL on these two cellular processes. Two separate effects of VLDL on peripheral blood mononuclear cell (PBM) cyclic adenosine monophosphate (AMP) metabolism were observed at VLDL concentrations which inhibit phytohemagglutinin (PHA)-induced [³H]thymidine uptake. VLDL suppressed the early, transient increase in PBM cyclic AMP which occurs within minutes of the addition of mitogen. VLDL exposure also stimulated a delayed (greater than 24 hr) and spontaneous increase in PBM cyclic AMP levels which corresponded temporally with progressive cellular refractoriness to mitogen stimulation. If mitogen-induced lymphoproliferation is influenced by early changes in cyclic nucleotide metabolism, as claimed by some investigators, then perhaps the ability of VLDL to modulate intracellular cyclic AMP levels may explain some of the antiproliferative properties of this bioregulatory lipoprotein.     

Chemical sympathectomy with 6-hydroxydopamine potentiates intracerebroventricularly applied bombesin-induced increase in plasma adrenaline

Intracerebroventricular administration of bombesin induced a marked increase in plasma level of adrenaline and a slight increase in that of noradrenaline in rats anesthetized with urethane. The bombesin-induced increase in adrenaline was potentiated by chemical sympathectomy with 6-hydroxydopamine (6-OHDA). On the other hand, adrenalectomy did not affect plasma level of noradrenaline in the bombesin-treated animals. In the splanchnicotomized rats, direct stimulation of the adrenal glands by intravenously administered nicotine increased plasma level of both adrenaline and noradrenaline. These increases were, however, not potentiated by chemical sympathectomy with 6-OHDA. Pretreatment with capsaicin, a potent toxin selective to sensory neurons, potentiated the bombesin-induced increase in plasma level of adrenaline. In these capsaicin pretreated rats, chemical sympathectomy did not potentiate the bombesin-induced increase in plasma level of adrenaline to any great extent. These results suggest that chemical sympathectomy with 6-OHDA potentiated the bombesin-induced increase in plasma adrenaline probably due to a disinhibitory activation of the splanchnic nerve by as yet unidentified but capsaicin sensitive neuron mechanisms.     

Determination of the adrenergic response by measurement of catecholamines and activity of dopamine-beta-hydroxylase (D-beta-B) in arterial capillary blood]

Plasma dopamine-beta-hydroxylase activity and catecholamines (adrenaline and noradrenaline) level in venous blood taken from the cubital vein and in arterialized capillary blood taken from the ear lobe were measured before and after a maximal exercise on a treadmill in 14 healthy untrained volunteers. The authors have shown a good correlation between these parameters in venous blood and those in capillary blood. It is concluded that the determination of plasma dopamine-beta-hydroxylase activity and catecholamines level in arterialized capillary blood could be a valid measure of the sympathetic activity.     

Effect of acebutolol on plasma catecholamine concentrations in anesthetized dogs with ouabain-induced arrhythmias and its direct actions in vitro on the adrenal medulla

We have performed studies on blood hormone dynamics following intravenous administration of acebutolol, a newly synthesized beta-blocker, and its direct action on the adrenal medulla in vitro. Intravenous injection of acebutolol into anesthetized dogs almost doubled the plasma adrenaline and noradrenaline concentrations within 5 to 15 minutes, while renin activity was reduced to approximately two-thirds of the pre-administration level. When arrhythmia was induced in dogs with ouabain, the plasma adrenaline and noradrenaline levels increased to 220 +/- 109 and 392 +/- 84 pg/ml, respectively, from the basal levels of 44 +/- 24 and 140 +/- 43 pg/ml. The restoration of sinus rhythm following the administration of acebutolol was accompanied by a further increase in the plasma adrenaline and noradrenaline levels to 797 +/- 364 and 1226 +/- 263 pg/ml, respectively. A perifusion experiment indicated that acebutolol directly accelerated catecholamine release from the adrenal medulla in pigs.     

Effect of an industrial-frequency electromagnetic field on protein biosynthesic processes of embryonal fibroblasts in tissue culture

Using radioautography, the influence of the industrial frequency electromagnetic field (50 cps) (EMF i/f), with the tension of 50 and 150 kv/m was studied, on the synthesis of collagen and non-collagen proteins in cultured fibroblast-like human embryo cells in the presence and absense in the medium of adrenaline and of cyclic adenosine monophosphate (cAMP). The EMF depresses protein proportionally to its intesity and duration. The specific function of fibroblasts -- the synthesis of collagen -- is subject to this influence to a great extent. The preliminary administration of adrenaline or cAMP prevented the above changes. The cyclic AMP exerted a much stronger protective effect.     

Hydrolysis of guanosine and adenosine 3',5'-monophosphates by rat blood.

Cyclic nucleotide phosphodiesterase activity was measured in whole blood, plasma, and suspensions of platelets and erythrocytes from rats. In fresh whole blood, apparent phosphodiesterase activity was low, but it rose strikingly during the hour after blood withdrawal. The apparent phosphodiesterase activity in platelet-free plasma showed no such increase, but that in platelet-enriched plasma increased in parallel with that in whole blood. The apparent phosphodiesterase activity of blood or of platelet-enriched plasma also was increased markedly by sonication. The increase in rat blood phosphodiesterase activity with aging thus appeared to be due to damage of platelets. Most of the phosphodiesterase activity in rat erythrocytes and platelets was located in the soluble fraction of sonicated preparations, but the total enzyme activities from the two sources exhibited marked differences in substrate specificity. With erythrocyte preparations, the rate of hydrolysis of muM concentrations of cyclic AMP was approx. 50 times that of cyclic GMP, while with platelet preparations, cyclic GMP was hydrolyzed about 20 times faster than cyclic AMP at muM levels. The activity of phosphodiesterase in platelets was much greater than that in erythrocytes at all concentrations of both substrates.     

Evidence for hormonal imbalance after methadone treatment in pregnant and pseudopregnant rats

The effects of methadone (METH) on the plasma estriol level and hormonal target tissues' cyclic nucleotides (cAMP and cGMP) were investigated in pregnant and pseudopregnant rats. In the pregnant animals, METH (5 mg/kg/day), given once daily from Days 6 to 15 of gestation, significantly reduced the maternal body weight gain in association with an increase in the number of dams bearing resorptions (56%) and a significant reduction in fetal body weight (33%). An inhibition of the plasma estriol level by METH was observed on Day 9 of gestation. Stimulation of the sympatho-adrenal axis and hypothalamo-pituitary axis by acute METH administration was observed and correlated with a significant increase in the levels of cyclic nucleotides in the uterus and adrenal glands of pregnant rats. However, tolerance to METH effects on cyclic nucleotide levels developed by Day 15 of gestation. METH also depressed the fetal cyclic nucleotide levels on Days 12 and 15 of gestation. These findings suggest that METH had pronounced effects on hormonal secretion during pregnancy, and hormonal transport to or hormonal production by the fetuses. In contrast, METH did not exhibit any adverse effects on the hormonal and cyclic nucleotide levels of pseudopregnant rats with deciduoma formation; a model for the maternal compartment. These latter findings may reflect METH's adverse effects on the fetal compartment, and suggest the use of pseudopregnancy as a model to distinguish adverse drug effects between these compartments.     

Inhibition of cyclic AMP phosphodiesterase activity of human blood platelet membrane by ADP

Purified human blood platelet membrane showed the presence of one low Km (1.1 microM) and one high Km (5.0 microM) cyclic AMP phosphodiesterase(s). Incubation of platelet-rich plasma or gel-filtered platelets with ADP (4.0 microM), a well-known platelet aggregating agent, resulted in the inhibition of phosphodiesterase activity of the isolated membrane by 25% in 5 min at 23 degrees C. A Lineweaver-Burk plot of the enzymic activity of the membrane preparation showed that ADP specifically inhibited the low Km (1.1 microM) phosphodiesterase by reducing the Vmax from 241 to 176 pmol/mg per min with concomitant lowering of Km to 0.5 microM. In contrast, neither the high Km (5.0 microM) enzymic activity of the membrane preparation nor the phosphodiesterase activities of the cytosolic fraction of the ADP-treated platelets was affected. This effect of ADP, which was independent of platelet aggregation, reached maximal level within 5 min of incubation. When platelet-rich plasma was incubated longer in the presence of nucleotide, the inhibition of phosphodiesterase activity began to decrease, and after 20 min of incubation approx. 90% of the original enzymic activity was regained. The incubation of platelet-rich plasma with 4.0 microM ADP also increased the cyclic AMP level to twice the basal level. The effect of ADP on the phosphodiesterase activity could be demonstrated only by incubating the intact platelets with the nucleotide. The treatment of isolated membrane from platelets, previously unexposed to ADP, with the nucleotide did not inhibit the enzymic activity. The inhibition of phosphodiesterase by the nucleotide in the absence of stirring, as expected, resulted in the inhibition of platelet aggregation when these cells were subsequently stirred with 1-epinephrine or an increased concentration of ADP.     

Hormonal stimulation of adenosine 3',5'-cyclic monophosphate formation in cell-free particles and intact cells of smooth muscle in the aorta and femoral artery of rats during immubilization stress]

The ability of adrenaline and histamine to stimulate the formation of cyclic AMP was investigated in broken cell preparation and intact cells of smooth muscle of the aorta and femoral artery of rats which had been subjected to daily intermittent immobilization for 1, 3, and 17 weeks. It was found that this type of stress led to an instability of the blood pressure which was associated with an increase in the sensitivity of adenylate cyclase in the broken cell preparations from the arteries to adrenaline and histamine and with a heightened cyclic AMP response to the two hormones in the intact arterial smooth muscle cells. The sensitivity of cardiac adenylate cyclase for adrenaline remained unchanged.     

Rouleau formation of erythrocytes is influenced by thrombocytes

Thrombocytes are activated by shearing and influence possibly the flow properties of blood. Erythrocytes resuspended in platelet poor plasma show a significantly increased deformability as well as reduced aggregability after addition of ADP as well as adrenaline in comparison with control. In platelet rich plasma the aggregation of erythrocytes becomes enhanced. This is discussed in respect of a release of macromolecules of platelets.     

Adrenomedullary origin of the hindquarter vasodilation during the transposition response of the rat

Transposing a rat from the home cage to a new cage produces a cardiovascular response (transposition response) characterized by an increase in hindquarter blood flow with unchanged systemic arterial pressure. Arterial blood samples were collected from rats before and during this response for radioenzymatic assay of catecholamines. During the transposition response, the concentration of adrenaline and noradrenaline in plasma increased about six- and two-fold, respectively. Ablation of the adrenal medulla prevented these changes in plasma catecholamine concentration. Constant i.v. infusion of adrenaline, at rates producing a hindquarter flow approximately matching that observed during the transposition response, evoked an increase in plasma adrenaline concentration also approximately matching the increase observed during the transposition response. It is concluded that the increase in plasma adrenaline secreted from the adrenal medulla is the main cause of the increase in hindquarter blood flow in the transposition response.     

Dopamine modification of the Ca-component of the action potential in the neuron soma of the mollusk L. stagnalis

Dopamine has been found to decrease reversibly the action potential rising phase in identified L. stagnalis neurones. Using voltage-clamp and intracellular dialysis techniques it is shown that dopamine inhibits electroexcitable Ca-current, and changes in Ca-current determine those in the action potential shape. Serotonin and adrenaline influence the Ca-current in a similar way as dopamine does. Inhibition of Ca-conductance is found not to be related to possible effect of these neuromediators on intracellular level of free Ca ions or cyclic AMP.