Figure 2: Treatment of CHO cells with Forskolin #3828 increases cAMP concentration as detected by Cyclic AMP XP® Assay Kit #4339. CHO cells were seeded at 4x104 cells/well in a 96-well plate and incubated overnight. Cells were either left untreated or pretreated with 0.5 mM IBMX for 30 minutes prior to forskolin treatment (15 minutes) and lysed with 1X Cell Lysis Buffer #9803. The absorbance values (left) and percentage of activity (right) are shown above. The percentage of activity is calculated as follows: % activity=100x[(A-Abasal)/(Amax-Abasal)], where A is the sample absorbance, Amax is the absorbance at maximum stimulation (i.e., high forskolin concentration), and Abasal is the absorbance at basal level (no forskolin). Forskolin directly activates adenylyl cyclases and increases cellular cAMP concentration. IBMX is a non-specific inhibitor of cAMP and cGMP phosphodiesterases and promotes accumulation of cAMP and cGMP in cells.
Figure 3: Treatment of 293 cells with isoproterenol increases the cAMP concentration as detected by Cyclic AMP XP® Assay Kit #4339. 293 cells were seeded at 3x104 cells/well in a 96-well plate and incubated overnight. Cells were pretreated with 0.5 mM IBMX for 30 minutes prior to isoproterenol treatment (3 minutes) and lysed with 1X Cell Lysis Buffer #9803. The absorbance values (left) and percentage of activity (right) are shown above. The percentage of activity is calculated as follow: % activity=100*[(A-Abasal)/(Amax-Abasal)], where A is the absorbance of the sample, Amax is the absorbance at maximum stimulation (i.e., high isoproterenol concentration), and Abasal is the absorbance at basal level (no isoproterenol). Isopropterenol is a β-adrenoceptor agonist and activates beta-2 adrenergic receptors (ADRB2) that are endogenously expressed on 293 cells. Activation of ADRB2 then leads to activation of adenylyl cyclase and synthesis of cAMP as its second messenger.
Figure 1: cAMP Standard was diluted in 1X Cell Lysis Buffer #9803 and samples were assayed following the Cyclic AMP XP® Assay Kit protocol. This standard curve is for demonstration purposes only; users should generate a standard curve for each sample set in order to accurately determine cAMP concentration.
|Product Includes||Quantity (with Count)||Solution Color|
|cAMP Rabbit mAb Coated Microwells||1 x 96 tests|
|cAMP-HRP Conjugate||1 x 11 ml||Red|
|cAMP Standard (2.4 uM)||1 x 1 ml|
|TMB Substrate 7004||1 x 11 ml|
|STOP Solution 7002||1 x 11 ml|
|Sealing Tape||1 x 2 ea|
|ELISA Wash Buffer (20X) 9801||1 x 10 ml|
|Cell Lysis Buffer (10X) 9803||1 x 15 ml|
NOTE: This procedure is for a 96-well tissue culture plate. It can be modified for other tissue culture plates (6, 12, 24, or 48 well).
NOTE: If cell debris is observed it can be removed by brief centrifugation of the plate and transfer of the clear lysates to a new 96 well plate.
NOTE: Watch the color as it being developed since it may be necessary to stop the reaction before 30 minutes.
NOTE: To determine the absolute amount of the tested substance, a standard curve needs to be generated each time. Please follow the detailed protocol on the product datasheet to determine the concentration range for the standard curve.
posted April 2010
Protocol Id: 68
The Cyclic AMP XP® Assay Kit is a competition enzyme-linked immunoassay used to determine cAMP levels in cells or tissues of interest. In this assay, cAMP found in test sample competes with a fixed amount of HRP-linked cAMP for binding to an anti-cAMP XP® Rabbit mAb immobilized onto a 96-well plate. Following washing to remove excess sample cAMP and HRP-linked cAMP, HRP substrate TMB is added to develop color. Because of the competitive nature of this assay, the magnitude of the absorbance for this developed color is inversely proportional to the quantity of sample cAMP. Measurement of absorbance using the cAMP Standard allows calculating the absolute amount of cAMP in a sample of interest.
Note: 12, 8-well modules -Each module is designed to break apart for 8 tests.
The immunoreactivity of this kit was tested against the following: ADP, AMP, ATP, cAMP, cGMP, cIMP, cTMP, CTP, GDP, GMP and GTP. Relatively minor cross-reactivity was observed with cGMP and cIMP, with 10 fold higher sensitivity for cAMP compared to either cGMP or cIMP. No cross-reactivity was observed with any of the other factors tested. Kit sensitivity, as shown in Figure 1, demonstrates a dynamic range of 0.2 to 12 nM of cAMP. Changes in cellular cAMP levels following specific treatments are shown in Figure 2 (CHO cells) and Figure 3 (293 cells).
All Species Expected
Cyclic adenosine 3’,5’-monophosphate (cAMP) is an important second messenger involved in many signal transduction pathways in different cell types of numerous species (1-3). In mammalian cells this important molecule is produced by adenylyl cyclases (AC). Extracellular stimuli such as neurotransmitters, hormones, chemokines, lipid mediators and drugs, can modulate AC activity to increase or decrease cAMP production by binding to a large number of transmembrane G protein-coupled receptors (4). The degradation of cAMP to AMP is catalyzed by phosphodiesterases that are regulated by intracellular nucleotide concentrations, phosphorylation, or binding of Ca2+/calmodulin and other regulatory proteins (5). A set of diverse molecules, including cAMP-dependent protein kinase (PKA), cyclic nucleotide-gated ion channels, and exchange proteins that are activated by cAMP (Epac), mediate downstream cAMP signaling (6,7). cAMP modulates various biological processes including metabolism, differentiation, cardiac cell functions, neuronal signaling, cell adhesion, and immune functions (5-7).
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