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Published on: November 27, 2016
Hydroxytryptamine transport by the bovine chromaffin-granule membrane
The Biochemical Journal
|March 15, 1978
Summary
Chromaffin granule ghosts accumulate 5-hydroxytryptamine using a pH gradient, similar to catecholamine uptake. This process is sensitive to reserpine, uncouplers, and permeant anions.
Area of Science:
- Neuroscience
- Biochemistry
- Cell Biology
Background:
- Chromaffin granules store catecholamines and serotonin.
- Granule membranes maintain internal pH gradients crucial for storage.
Purpose of the Study:
- To investigate the role of pH gradients in 5-hydroxytryptamine (serotonin) uptake by chromaffin granule ghosts.
- To determine the sensitivity of this uptake mechanism to various inhibitors and conditions.
Main Methods:
- Utilized resealed chromaffin-granule 'ghosts' with imposed pH gradients (acidic interior).
- Assessed 5-hydroxytryptamine accumulation under different conditions, including MgATP presence, reserpine, uncouplers, nigericin, and permeant anions.
- Measured the effect of 5-hydroxytryptamine on MgATP-generated pH gradients.
Main Results:
- 5-Hydroxytryptamine uptake occurred when an acidic interior pH gradient was established.
- Uptake was sensitive to reserpine and uncouplers, mirroring MgATP-driven catecholamine transport.
- 5-Hydroxytryptamine reduced the MgATP-generated pH gradient, an effect blocked by reserpine.
- Nigericin and permeant anions inhibited uptake, suggesting disruption of the pH gradient or direct amine equilibration.
Conclusions:
- A pH gradient (acidic inside) is a primary driving force for 5-hydroxytryptamine accumulation in chromaffin granule ghosts.
- The uptake mechanism shares similarities with catecholamine transport, involving reserpine-sensitive processes.
- Permeant anions may inhibit uptake by facilitating direct amine cation equilibration across the membrane.
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