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A dopamine transporter in human erythrocytes: modulation by insulin
R Azoui1, J L Cuche, J F Renaud
1INSERM Unité 337, Department of Internal Medicine, Broussais-Hotel-Dieu, Faculty of Medicine, Paris, France.
Experimental Physiology
|May 1, 1996
Summary
Human red blood cells transport catecholamines like dopamine via a choline exchanger. Insulin regulates this transport, suggesting red blood cells act as a storage site for circulating catecholamines.
Area of Science:
- Physiology
- Biochemistry
- Pharmacology
Background:
- Red blood cells (RBCs) possess the capability to transport and accumulate catecholamines.
- Understanding the specific mechanisms of catecholamine transport in RBCs is crucial for comprehending their role in overall catecholamine homeostasis.
Purpose of the Study:
- To characterize the catecholamine transport system in human RBCs, with a specific focus on dopamine.
- To investigate the potential involvement of known transporters and the influence of insulin on this process.
Main Methods:
- Kinetic analysis of dopamine, noradrenaline, and adrenaline influx into RBCs.
- Assessment of transport inhibition using various pharmacological agents (e.g., DMA, DIDS, reserpine, GBR 12909, GBR 12935, cyanine, probenecid).
- Investigation of the effect of choline and insulin on catecholamine transport.
Main Results:
- Catecholamine influx into RBCs exhibited saturation kinetics, indicating a carrier-mediated process.
- Transport was not mediated by Na(+)-H+ exchanger, anion exchanger, or synaptosomal/proximal tubule dopamine transporters.
- Dopamine transport was identified as potentially occurring via the choline exchanger, inhibited by probenecid.
- Insulin significantly reduced catecholamine influx in fasting subjects, but not in fed subjects, suggesting insulin-dependent regulation.
Conclusions:
- Human RBCs transport catecholamines, particularly dopamine, via an exchanger system, likely the choline transporter.
- Insulin plays a regulatory role in catecholamine transport across RBC membranes.
- These findings support the role of RBCs as a significant storage pool for circulating catecholamines.