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Choline transport in rat liver basolateral plasma membrane vesicles
R H Moseley1, H Takeda, L J Zugger
1Department of Internal Medicine, Veterans Affairs Medical Center, Ann Arbor, MI 48105, USA.
Hepatology (Baltimore, Md.)
|July 1, 1996
Summary
This study reveals an electrogenic pathway for choline uptake in rat liver basolateral membranes, driven by membrane potential, not ion gradients. This finding highlights diverse mechanisms for organic cation transport.
Area of Science:
- * Biochemistry and Molecular Biology
- * Cell Physiology
- * Membrane Transport
Background:
- * Multiple pathways exist for organic cation uptake in the liver.
- * These include H+ exchange and membrane potential-driven systems.
- * The specific mechanisms for endogenous choline uptake are not fully elucidated.
Purpose of the Study:
- * To determine the driving forces for choline uptake in rat liver basolateral plasma membrane (blLPM) vesicles.
- * To characterize the transport mechanism of choline at the sinusoidal membrane.
Main Methods:
- * Utilized rat liver blLPM vesicles to study choline uptake.
- * Manipulated ion gradients (H+, Na+, K+) and membrane potential to assess transport drivers.
- * Investigated kinetic parameters (Km, Vmax) and inhibition profiles.
Main Results:
- * Choline uptake was driven by an inside-negative K+ diffusion potential, indicating an electrogenic pathway.
- * Uptake exhibited temperature dependency, trans-stimulation, and saturability (Km ≈ 0.34 mmol/L, Vmax ≈ 0.45 nmol/mg protein/15 s).
- * Hemicholinium-3 and acetylcholine inhibited choline uptake, while other organic cations did not.
Conclusions:
- * Demonstrates an electrogenic pathway for choline uptake on the liver's sinusoidal membrane.
- * Supports the existence of multiple, distinct transport systems for organic cations in the liver.
- * Identifies a specific transport mechanism for the essential nutrient choline.
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