Norepinephrine:adenosinetriphosphate ratios in purified adrenergic vesicles.

Area of Science:

• Neuroscience
• Biochemistry
• Cell Biology

Background:

• Large dense core vesicles (LDCVs) in nerve terminals store neurotransmitters like norepinephrine (NE).
• The ratio of NE to adenosine triphosphate (ATP) within these vesicles is crucial for neurotransmission.
• Understanding how this ratio changes during vesicle maturation and post-mortem is important for accurate biochemical analysis.

Purpose of the Study:

• To investigate the norepinephrine (NE) to adenosine triphosphate (ATP) molar ratios in purified bovine splenic nerve vesicles.
• To examine how post-mortem time and animal weight affect NE and ATP content in these vesicles.
• To determine changes in the NE:ATP ratio during vesicle maturation along the axoplasmic transport pathway.

Main Methods:

• Isolation of highly purified large dense core vesicles from bovine splenic nerve.
• Comparison of NE:ATP ratios in vesicles chilled at different post-mortem times (10 vs. 30 min).
• Analysis of NE and ATP content in vesicles from animals of varying weights and from different nerve segments (proximal vs. distal).

Main Results:

• The NE:ATP molar ratio decreased significantly with increased post-mortem time (6.3 to 4.8) and with increasing animal weight (7.2 to 5.2).
• NE content increased with animal weight and along the nerve segment from proximal to distal (45 to 70 nmol), while ATP content remained relatively stable.
• Vesicle maturation showed an increased NE:ATP ratio (4.5 to 7.0) due to increased NE accumulation without a corresponding increase in ATP.

Conclusions:

• Vesicle ATP content appears to be established early in the neuron's cell body and remains constant during axoplasmic transport.
• Post-mortem hydrolysis affects NE levels more than ATP levels, decreasing the NE:ATP ratio.
• The observed increase in the NE:ATP ratio in distal vesicles suggests NE is added to a pre-existing ATP-containing pool during transport.