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Modulation of multidrug resistance protein (MRP1/ABCC1) expression: a novel physiological role for ouabain

R C Valente1, L S Capella, C R Nascimento

  • 1Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.

Cell Biology and Toxicology
|April 25, 2007
PubMed

Insights

The hormone ouabain affects the expression and function of the ATP binding cassette C1 (ABCC1) transporter. This hormonal regulation suggests a role for ABCC1 in body volume control and potential implications for cancer treatment.

Area of Science:

  • Biochemistry
  • Cell Biology
  • Endocrinology

Background:

  • Ouabain, a (Na(+),K(+))-ATPase inhibitor, modulates ATP binding cassette (ABC) transporters like ABCC7, ABCB1, and ABCC1.
  • ABCB1 is the only ABC transporter with a known physiological role in the kidney, involved in secretion.
  • The physiological role of ABCC1 and its interaction with endogenous hormones like ouabain remain largely unexplored.

Purpose of the Study:

  • To investigate the relationship between ouabain and the expression and function of ABCC1.
  • To establish a potential physiological role for ouabain in regulating ABCC1.

Main Methods:

  • Incubation of cells with varying concentrations and durations of ouabain.
  • Analysis of ABCC1 protein expression and mRNA levels.
  • Assessment of ABCC1 transporter activity using a fluorescent substrate (carboxyfluorescein diacetate).

Main Results:

  • Prolonged ouabain exposure (24 h) at 1 nmol/L or higher decreased ABCC1 protein expression while inducing its mRNA expression.
  • The observed decrease in ABCC1 protein was rapidly reversible upon removal of ouabain, indicating hormonal regulation.
  • Ouabain concentrations of 100 nmol/L or higher impaired ABCC1 activity, evidenced by increased carboxyfluorescein diacetate accumulation.

Conclusions:

  • Ouabain, as an endogenous hormone, regulates ABCC1 expression and function.
  • ABCC1 may be involved in hormonal regulation related to body volume control.
  • Findings suggest potential therapeutic implications for hypertensive cancer patients and highlight ABCC1's role in other tissues like the brain and immune system.

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