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Preparation of Highly Coupled Rat Heart Mitochondria
Published on: September 23, 2010
Release of AMP and adenosine from rat heart mitochondria
Abstract:
Release of AMP and adenosine from rat heart mitochondria was studied. The rate of appearance of extramitochondrial adenosine was independent of the extramitochondrial phosphate concentration between 5 and 20 mM. In the absence of exogenous, respiratory substrates or in the presence of glutamate/malate plus rotenone, the rate of appearance of adenosine was relatively low when phosphate was not added. The appearance of extramitochondrial AMP + adenosine was found to be directly proportional to the extra-mitochondrial phosphate concentration. Zn2+ (10 mM) decreased the rate of adenosine appearance by 90% and increased the rate of AMP appearance 6-fold. The mitochondrial preparations dephosphorylated exogenous AMP; this activity was inhibited by 10 mM Zn2+. We conclude that the adenosine appearing in the extramitochondrial space was not due to a direct release from the matrix, but instead was due to adenine nucleotide release with subsequent conversion to adenosine in the extramitochondrial space.
Insights
Mitochondria release adenine nucleotides, not adenosine, into the cell. Extramitochondrial enzymes then convert these nucleotides to adenosine, a process influenced by phosphate levels and zinc ions.
Area of Science:
- Mitochondrial biochemistry
- Cellular energy metabolism
- Nucleotide signaling
Background:
- Mitochondria play a crucial role in cellular energy production and signaling.
- The release of adenosine triphosphate (ATP) and its metabolites from mitochondria influences cellular processes.
- Understanding the mechanisms of adenine nucleotide and adenosine release is vital for comprehending cellular homeostasis.
Purpose of the Study:
- To investigate the release mechanisms of adenosine monophosphate (AMP) and adenosine from rat heart mitochondria.
- To determine the factors influencing the rate and origin of extramitochondrial adenosine production.
Main Methods:
- Studied AMP and adenosine release from isolated rat heart mitochondria under varying conditions.
- Assessed the impact of phosphate concentration, respiratory substrates, and zinc ions (Zn2+) on release rates.
- Investigated the dephosphorylation of exogenous AMP by mitochondrial preparations.
Main Results:
- Extramitochondrial adenosine appearance was independent of phosphate concentration (5-20 mM) but dependent on adenine nucleotide release.
- Adenine nucleotide (AMP + adenosine) appearance correlated directly with extramitochondrial phosphate.
- Zinc ions significantly inhibited adenosine release while increasing AMP release, suggesting AMP dephosphorylation is zinc-sensitive.
Conclusions:
- Adenosine observed in the extramitochondrial space originates from released adenine nucleotides, not direct matrix release.
- Extramitochondrial enzymes are responsible for converting released adenine nucleotides to adenosine.
- Phosphate concentration and zinc ions modulate the release and conversion of adenine nucleotides to adenosine.
