Na(+)-I- symport activity is present in membrane vesicles from thyrotropin-deprived non-I(-)-transporting cultured thyroid cells. Academic Article uri icon

Overview

MeSH

  • Animals
  • Biological Transport
  • Cell Line
  • Cell Membrane
  • Cell-Free System
  • In Vitro Techniques
  • Rats
  • Thyrotropin

MeSH Major

  • Carrier Proteins
  • Iodides
  • Membrane Proteins
  • Sodium
  • Symporters
  • Thyroid Gland

abstract

  • The active accumulation of I- in the thyroid gland is mediated by the Na(+)-I- symporter and driven by the Na+ gradient generated by the Na+/K(+)-ATPase. Thyrotropin (TSH) stimulates thyroidal I- accumulation. Rat thyroid-derived FRTL-5 cells require TSH to accumulate I-. TSH withdrawal for over 7 days results in complete loss of Na(+)-I-symport activity in these cells [Weiss, S. J., Philp, N. J. and Grollman, E. F. (1984) Endocrinology 114, 1090-1098]. Surprisingly, membrane vesicles prepared from FRTL-5 cells maintained in TSH-free medium [TSH(-)cells]accumulate I-, suggesting that the absence of Na(+)-I- symport activity in TSH(-) cells cannot be due solely to a decrease in the biosynthesis of either the symporter or a putative activating factor. This finding indicates that the Na(+)-I- symporter is present, probably in an inactive state, in TSH(-) cells despite their lack of Na(+)-I- symport activity. Na(+)-I- symport activity in thyroid membrane vesicles is enhanced when conditions for vesicle preparation favor proteolysis. Subcellular fractionation studies in both TSH(+) and TSH(-) cells show that Na(+)-I- symport activity is mostly associated with fractions enriched in plasma membrane rather than in intracellular membranes, suggesting that the Na(+)-I- symporter may constitutively reside in the plasma membrane and may be activated by TSH.

publication date

  • April 26, 1994

has subject area

  • Animals
  • Biological Transport
  • Carrier Proteins
  • Cell Line
  • Cell Membrane
  • Cell-Free System
  • In Vitro Techniques
  • Iodides
  • Membrane Proteins
  • Rats
  • Sodium
  • Symporters
  • Thyroid Gland
  • Thyrotropin

Research

keywords

  • Journal Article

Identity

Language

  • eng

PubMed Central ID

  • PMC43667

PubMed ID

  • 8170988

Additional Document Info

start page

  • 3789

end page

  • 3793

volume

  • 91

number

  • 9