Related Experiment Videos
Identification and characterization of adenosine A1 receptor-cAMP system in human glomeruli
1Second Department of Internal Medicine, Yokohama City University, School of Medicine, Japan.
Abstract:
Although adenosine is known to affect renal function through stimulating adenosine receptors, little is known about A1 receptors in human glomeruli. Thus, we attempted to identify the adenosine A1 receptor-cyclic AMP (cAMP) system in human glomeruli. Normal renal cortical tissues were obtained at nephrectomy of patients with renal cell carcinoma. Glomeruli were isolated using a graded sieving method or dissected manually under a stereomicroscope. Radioligand binding assay using 2-chloro-N-[3H] cyclopentyl adenosine ([3H]CCPA, an A1 agonist ligand) was performed at 30 degrees C for 90 minutes. Cyclic AMP (cAMP) produced in glomeruli was measured after incubation with different concentrations of N6-cyclohexyladenosine (CHA; A1 agonist) and a phosphodiesterase inhibitor. The specific binding was saturated within 60 minutes and reversible by adding 1 mM of theophylline. Scatchard plot analysis revealed a single class of binding site (Kd = 1.78 +/- 0.21 nM, Bmax = 271.7 +/- 35.8 fmol/mg protein). The specific binding was inhibited dose-dependently by various agents in an order suggesting A1 receptor specificity. CHA inhibited the production of cAMP in microdissected human glomeruli. This inhibitory effect was antagonized by 8-cyclopentyl-1,3-dipropylxanthine (DPCPX; A1 antagonist). This is the first study revealing the presence of the A1 receptor-cAMP system in human glomeruli using a radioligand binding assay method and by measuring the cAMP production.
Insights
This study identifies the adenosine A1 receptor-cyclic AMP (cAMP) system in human glomeruli. Researchers confirmed the presence and function of these receptors, crucial for understanding kidney physiology.
Area of Science:
- Nephrology
- Molecular Biology
- Pharmacology
Background:
- Adenosine influences renal function via adenosine receptors.
- The role of A1 receptors in human glomeruli remains largely uncharacterized.
Purpose of the Study:
- To identify and characterize the adenosine A1 receptor-cyclic AMP (cAMP) system in human glomeruli.
Main Methods:
- Utilized radioligand binding assays with [3H]CCPA to identify A1 receptors in isolated human glomeruli.
- Measured cAMP production in response to A1 receptor agonists (CHA) and antagonists (DPCPX).
- Employed Scatchard plot analysis to determine binding kinetics (Kd, Bmax).
Main Results:
- Demonstrated specific binding sites for A1 receptors in human glomeruli.
- Confirmed dose-dependent inhibition of cAMP production by A1 agonists, antagonized by A1 antagonists.
- Characterized the binding affinity (Kd = 1.78 +/- 0.21 nM) and density (Bmax = 271.7 +/- 35.8 fmol/mg protein).
Conclusions:
- This study provides the first evidence for the presence and functional activity of the A1 receptor-cAMP system in human glomeruli.
- Findings are significant for understanding adenosine's role in human kidney physiology and potential therapeutic targets.