Related Experiment Video
Updated: Aug 15, 2026
11:13
Dissection of Adult Mouse Utricle and Adenovirus-mediated Supporting-cell Infection
Published on: March 28, 2012
Ecto-nucleotidases terminate purinergic signalling in the cochlear endolymphatic compartment
S M Vlajkovic1, P R Thorne, G D Housley
1Department of Physiology, University of Auckland, New Zealand.
Neuroreport
|June 19, 1998
Summary
Ecto-nucleotidases terminate purinergic signaling in the cochlear endolymphatic compartment. This study reveals their role in regulating auditory sensitivity by degrading extracellular ATP to adenosine.
Area of Science:
- Oto-neuroscience
- Cellular and Molecular Biology
- Biochemistry
Background:
- Purinergic signaling plays a crucial role in regulating auditory sensitivity in the inner ear.
- The precise mechanisms for terminating purinergic signaling within the cochlear endolymphatic compartment remain incompletely understood.
Purpose of the Study:
- To investigate the role of ecto-nucleotidases in the termination of purinergic signaling within the scala media (SM) of the guinea-pig cochlea.
- To characterize the enzymatic activity responsible for extracellular adenosine triphosphate (ATP) degradation.
Main Methods:
- Isolated, perfused guinea-pig cochlea model.
- Introduction of exogenous ATP into the scala media (SM).
- Analysis of adenine nucleotide metabolites in effluent using reverse-phase High-Performance Liquid Chromatography (HPLC).
- Assessment of tissue viability via fluorescence imaging.
- Pharmacological inhibition studies using Ca2+/Mg2+, azide, and suramin.
Main Results:
- Extracellular ATP was efficiently degraded to adenosine in the SM.
- ATP degradation was dependent on Ca2+/Mg2+ ions.
- The process was not inhibited by intracellular ATPase or non-specific alkaline phosphatase inhibitors.
- High azide concentration and suramin inhibited ATP hydrolysis, suggesting E-type ATPase involvement.
- High Vmax of ATP hydrolysis indicated significant ecto-ATPase activity.
Conclusions:
- Ecto-nucleotidases are a primary mechanism for terminating purinergic signaling in the cochlear scala media (SM).
- This enzymatic activity is crucial for modulating purinergic neurotransmission in a cochlear compartment with high P2X receptor expression.
- Understanding these mechanisms may offer insights into auditory function and dysfunction.
Related Concept Videos
01:22Hair Cells
Hair cells are the sensory receptors of the auditory system—they transduce mechanical sound waves into electrical energy that the nervous system can understand. Hair cells are located in the organ of Corti within the cochlea of the inner ear, between the basilar and tectorial membranes. The actual sensory receptors are called inner hair cells. The outer hair cells serve other functions, such as sound amplification in the cochlea, and are not discussed in detail here.
01:13The Cochlea
The cochlea is a coiled structure in the inner ear that contains hair cells—the sensory receptors of the auditory system. Sound waves are transmitted to the cochlea by small bones attached to the eardrum called the ossicles, which vibrate the oval window that leads to the inner ear. This causes fluid in the chambers of the cochlea to move, vibrating the basilar membrane.
02:27Nonsense-mediated mRNA Decay
The Upf proteins that carry out nonsense-mediated decay (NMD) are found in all eukaryotic organisms, including humans. Each protein has an individual role, but they need to work in collaboration. Upf1 is an ATP-dependent RNA helicase that unwinds the RNA helix. Because Upf1 can unwind any RNA, Upf2 and Upf3 are required to help Upf1 discriminate between nonsense and normal mRNAs.
Usually, Upf3 binds to an Exon Junction Complex (EJC) at mRNA splice sites. If a ribosome fully translates the mRNA,...
Usually, Upf3 binds to an Exon Junction Complex (EJC) at mRNA splice sites. If a ribosome fully translates the mRNA,...
01:22Amplifying Signals via Enzymatic Cascade
When a ligand binds to a cell-surface receptor, the receptor's intracellular domain changes shape, which may either activate its enzyme function or allow its binding to other molecules. The initial signal is amplified by most signal transduction pathways. This means that a single ligand molecule can activate multiple molecules of a downstream target. Proteins that relay a signal are most commonly phosphorylated at one or more sites, activating or inactivating the protein. Kinases catalyze the...
01:15Auditory Pathway
Auditory pathways constitute the complex neural circuits responsible for transmitting and interpreting auditory information from the peripheral auditory system to the brain. Sound waves are initially captured by the outer ear, funneled through the ear canal, and reach the tympanic membrane (eardrum). These vibrations are transmitted via the middle ear's ossicles to the inner ear's cochlea.
When viewed cross-sectionally, the cochlea reveals the scala vestibuli and scala tympani flanking the...
When viewed cross-sectionally, the cochlea reveals the scala vestibuli and scala tympani flanking the...
01:28Biosynthesis of Nucleic Acids
Nucleic acid biosynthesis is a fundamental biochemical process that produces the purine and pyrimidine nucleotides essential for DNA and RNA synthesis. This pathway maintains a balanced nucleotide pool, preventing imbalances that could jeopardize genetic integrity and cellular function. Given the crucial role of nucleotides, their synthesis is tightly regulated to ensure proper cellular homeostasis.Purine BiosynthesisThe biosynthesis of purine nucleotides begins with ribose-5-phosphate, a...