Effect Of Ionophore A23187 Research Articles

Metabolic aspects of the secretion of stored compounds from blood platelets. V. Effect of ionophore A23187 on washed platelets.

1. The A23187-induced secretion of preabsorbed serotonin from human blood platelets at 37 degrees C is studied. Preincubation at the same temperature before the addition of ionophore is necessary for maximal release induction. When total incubation time is kept constant, longer time with ionophore results in a smaller decrease in the level of metabolic ATP and increase in metabolic ATP and increase in metabolic IMP. This coincides with the reduction in secretion, but statistical treatment of the results suggests that the reduced secretion only partially explains the reduced drop in metabolic ATP, and that therefore a resynthesis of metabolic ATP from IMP may have taken place. 2. In some experiments induction of secretion takes place over a very narrow range of ionophore concentration. 3. When K+ substitutes for Na+ in the extracellular medium, the need for preincubation for maximal secretion becomes less evident, and at times is abolished, while there is still a significant increase in the metabolic ATP level by prolonged incubation with ionophore. 4. A reduction in secretion is observed with metabolic blockers when the ionophore is added after preincubation, but to a much less degree than when secretion is induced by thrombin, in spite of a great reduction in the level of metabolic ATP. This may partly be explained by the increase in secretion induction by A23187 in the presence of inhibitors when the ionophore is added in the cold, suggesting that the inhibitor may cause "weakening" of the platelets' "resistance" to induction of secretion by ionophore. 5. When the effect of Ca2+ and of Mg2+ on the level of intermediates of the TP leads to hypoxanthine conversion is studied, it is evident that the addition of Ca2+ causes enhanced IMP accumulation and a reduction in the level of inosine plus hypoxanthine, while Mg2+ has the opposite effect. This suggests that the two metals affect the enzymes of the IMP leads to hypoxanthine conversion differently. 6. Indomethacin inhibits secretion induced by A23187, suggesting that prostaglandin intermediates may amplify the ionophore-induced release. The adenine nucleotide metabolism is not affected. 7. The results indicate that there is an indirect, rather than direct, link between the major metabolic changes and the secretion induced by A23187, but that the ionophore may cause intracellular changes which are not connected to its effect as release inducer.

Calcium-dependent regulation of guanosine 3′,5′-monophosphate in renal cortex: Effects of ionophore A23187 and tetracaine and evidence for independent control of adenosine 3′,5′-monophosphate

The effects of carbamylcholine (Cch), the divalent cation ionophore A23187 and Ca 2+ on the cyclic 3′,5′-guanosine monophosphate (cGMP) and cyclic 3′,5′-adenosine monophosphate (cAMP) content of rat renal cortical slices were examined. In both the presence and absence of 10 m M theophylline, Cch detectably increased cGMP within 15 sec, with peak responses noted by 2 min. The maximal cGMP response to Cch alone (0.05 m M) was an increase of two- to three-fold over control. Theophylline, which was routinely present in the incubations and which alone increased cGMP of the slices two-fold over basal during 20 min incubations, potentiated the response to Cch (maximal increase, five- to sixfold over theophylline alone). The action of Cch to increase renal cortical cGMP was blocked by prior addition of atropine and was dependent upon the presence of Ca 2+ in the incubation media. Exclusion of Ca 2+ lowered basal cGMP and abolished increases mediated by Cch, while exclusion of Mg 2+ was without detectable effect on cGMP. In slices incubated initially without Ca 2+, reexposure to Ca 2+ for 1 min partially restored the cGMP response to Cch, and reexposure for 3 min completely restored this response. Since prior incubation of tissue in Ca 2+-free buffer for only 2 min was sufficient to block the cGMP responses to Cch, depletion of tissue Ca 2+ did not appear to be involved. A23187 also increased renal cortical cGMP fivefold in the presence of Ca 2+. Its effects were not additive with those of Cch and were not expressed by Mg 2+ in Ca 2+-free media. By contrast, tetracaine, which blocks Ca 2+ transport across or binding to biologic membranes, reduced basal cGMP and inhibited the actions of Cch and A23187 to increase cGMP in cortical slices incubated with Ca 2+. The action of 1 mM tetracaine to block Cch-mediated increases in cGMP was partially reversed by increasing media Ca 2+ from 1.5 to 5 m M, but not by increasing media Mg 2+ to 5 m M. In contrast to their effects on cGMP, Cch, A23187, Ca 2+ exclusion, and tetracaine did not detectably alter basal renal cortical cAMP or cAMP responses to parathyroid hormone (PTH). Conversely, concentrations of PTH, glucagon, and isoproterenol which maximally increased renal cortical cAMP did not alter cGMP. Furthermore, prior incubation of slices with Cch did not alter their subsequent cAMP response to PTH at a time when cGMP levels were still elevated, while prior incubation with PTH did not affect the subsequent cGMP response to Cch at a time when cAMP was increased. These studies demonstrate modulation of renal cortical cGMP by cholinergic stimuli and Ca 2+. They also indicate that cGMP and cAMP in renal cortex can be regulated independently.

The effect of intracellular calcium ions on adrenaline-stimulated adenosine 3′:5′-cyclic monophosphate concentrations in pigeon erythrocytes, studied by using the ionophore A23187

1. The bivalent cation ionophore A23187 was used to increase the intracellular concentration of Ca2+ in pigeon erythrocytes to investigate whether the increase in cyclic AMP content caused by adrenaline might be influenced by a change in intracellular Ca2+ in intact cells. 2. Incubation of cells with adrenaline, in the concentration range 0.55--55 muM, resulted in an increase in the concentration of cyclic AMP over a period of 60 min. The effect of adrenaline was inhibited by more than 90% with ionophore A23187 (1.9 muM) in the presence of 1 mM-Ca2+. This inhibition could be decreased by decreasing either the concentration of the ionophore or the concentration of extracellular Ca2+, and was independent of the concentration of adrenaline. 3. The effect of ionophore A23187 depended on the time of incubation. Time-course studies showed that maximum inhibition by ionophore A23187 was only observed when the cells were incubated with the ionophore for at least 15 min before the addition of adrenaline. 4. The inhibition by ionophore A23187 depended on the concentration of extracellular Ca2+. In the absence of Mg2+, ionophore A23187 (1.9 muM) inhibited the effect of adrenaline by approx. 30% without added Ca2+, by approx. 66% with 10 muM-Ca2+ and by more than 90% with concentrations of added Ca2+ greater than 30 muM. However, even in the presence of EGTA [ethanedioxybis(ethylamine)tetra-acetate](0.1--10 mM), ionophore A23187 caused an inhibition of the cyclic AMP response of at least 30%, which may have been due to a decrease in cell Mg2+ concentration. 5. The addition of EGTA after incubation of cells with ionophore A23187 resulted in a partial reversal of the inhibition of the effect of adrenaline. 6. Inclusion of Mg2+ (2 mM) in the incubation medium antagonized the inhibitory action of ionophore A23187. This effect was most marked when the ionophore A23187 was added to medium containing Mg2+ before the addition of the cells. 7. The cellular content of Mg2+ was decreased by approx. 50% after 20 min incubation with ionophore A23187 (1.9 muM) in the presence of Ca2+ (1 mM) but no Mg2+. When Mg2+ (2 mM) was also present in the medium, ionophore A23187 caused an increase of approx. 80% in cell Mg2+ content. Ionophore A23187 had no significant effect on cell K+ content. 8. Ionophore A23187 caused a decrease in cell ATP content under some conditions. Since effects on cyclic AMP content could also be shown when ATP was not significanlty lowered, it appeared that a decrease in ATP in the cells could not explain the effect of ionophore A23187 on cyclic AMP. 9. Ionophore A23187 (1.9 muM), with 1 mM-Ca2+, did not enhance cyclic AMP degradation in intact cells, suggesting that the effect of ionophore A23187 on cyclic AMP content was mediated through an inhibition of adenylate cyclase rather than a stimulation of cyclic AMP phosphodiesterase. 10. It was concluded that in intact pigeon erythrocytes adenylate cyclase may be inhibited by intracellular concentrations of Ca2+ in the range 1-10 muM.

The effects of ionophore A23187 on erythrocytes relationship of ATP and 2,3-diphosphoglycerate to calcium-binding capacity

The divalent cation ionophore, A23187, was employed as a means to load fresh human erythrocytes with calcium, and the capacity for accumulation was characterized. Erythrocytes exposed to A23187 in calcium-containing media rapidly accumulated calcium in millimolar quantities. The final cellular concentration was dependent upon medium calcium concentration and the size of the cellular organophosphate pool. When ATP and 2,3-diphosphoglycerate contents were depleted or repleted, the cellular calcium content changed proportionally. Calcium loading of fresh erythrocytes produced no discernible change in the cellular concentrations of ATP or 2,3-diphosphoglycerate. Calcium accumulation was also accompanied by loss of cellular potassium and H 2O, deterioration of cell filterability, and spheroechinocytic transformation.

Endogenous prostaglandins and osmotic water flow in the toad bladder.

Endogenous prostaglandins and osmotic water flow in the toad bladder.

Effect of 3',5'-GMP and 3',5'-IMP on production of glucose and ammonia by renal cortex.

ARTICLESEffect of 3',5'-GMP and 3',5'-IMP on production of glucose and ammonia by renal cortexAS Pagliara, and AD GoodmanAS Pagliara, and AD GoodmanPublished Online:01 May 1970https://doi.org/10.1152/ajplegacy.1970.218.5.1301MoreSectionsPDF (1 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByDesign fabrication of electrochemical sensor based on Ru(bpy)22+/SMWCNTs/Au/GCE electrode for the selective determination of 5′-guanosine monophosphateFood Chemistry, Vol. 105An electrochemical sensor based on [Ru(bpy)2dpp]2+/SMWCNTs/Au modified glassy carbon electrode for the detection of 5ʹ-GMP3 August 2022 | Applied Biological Chemistry, Vol. 65, No. 1Hormonal mediators of ammoniagenesis: Mechanism of action of PGF2α and the implications for other hormonesKidney International, Vol. 50, No. 1Stimulation of renal gluconeogenesis by angiotensin IIBiochimica et Biophysica Acta (BBA) - General Subjects, Vol. 584, No. 3Alterations in rat renal cortical and medullary guanosine 3′5′-monophosphate accumulation by oxygen- and calcium-dependent and -independent mechanisms: Evidence for a calcium-independent action of oxygen in renal inner medullaMetabolism, Vol. 27, No. 7Calcium-dependent regulation of guanosine 3′,5′-monophosphate in renal cortex: Effects of ionophore A23187 and tetracaine and evidence for independent control of adenosine 3′,5′-monophosphateMetabolism, Vol. 25, No. 10Cyclic AMP and cyclic GMP: Studies utilizing immunohistochemical techniques for the localization of the nucleotides in tissueMetabolism, Vol. 24, No. 3Metabolism of Isolated Kidney Tubules Independent Actions of Catecholamines on Renal Cyclic Adenosine 3': 5'-Monophosphate Levels and GluconeogenesisEuropean Journal of Biochemistry, Vol. 52, No. 2Effects of adrenergic nervous system and catecholamines on systemic and renal hemodynamics, sodium and water excretion and renin secretionKidney International, Vol. 6, No. 5Sympathetic-parasympathetic interactions on the ventricular myocardium: possible role of cyclic nucleotidesBasic Research in Cardiology, Vol. 69, No. 3Guanine nucleotides and their significance in biochemical processesThe American Journal of Clinical Nutrition, Vol. 27, No. 4Cyclic guanosine-3??5?-monophosphate induced diuresis in ratsNaunyn-Schmiedeberg's Archives of Pharmacology, Vol. 284, No. 2Beeinflussung der Insulinkonzentration im Serum von Ratten durch Analoga von Adenosin-3′,5′-monophosphatResearch in Experimental Medicine, Vol. 160, No. 4Synthesis and biochemical studies of various 8-substituted derivatives of guanosine cyclic-3',5' phosphate, inosine cyclic-3',5' phosphate, and xanthosine cyclic-3',5' phosphate1 May 2002 | Biochemistry, Vol. 12, No. 26Effects of catecholamines on ammoniagenesis and gluconeogenesis by renal cortex in vitroBiochimica et Biophysica Acta (BBA) - General Subjects, Vol. 304, No. 1REFERENCESChapter 21. Biological Actions of Cyclic AMP Analogs More from this issue > Volume 218Issue 5May 1970Pages 1301-1306 Copyright & PermissionsCopyright © 1970 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1970.218.5.1301PubMed5438254History Published online 1 May 1970 Published in print 1 May 1970 Metrics