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Mechanism of liver-selective thyromimetic activity of SK&F L-94901: evidence for the presence of a cell-type-specific nuclear iodothyronine transport process.

Authors
  • Ichikawa, K
  • Miyamoto, T
  • Kakizawa, T
  • Suzuki, S
  • Kaneko, A
  • Mori, J
  • Hara, M
  • Kumagai, M
  • Takeda, T
  • Hashizume, K
Type
Published Article
Journal
The Journal of endocrinology
Publication Date
May 01, 2000
Volume
165
Issue
2
Pages
391–397
Identifiers
PMID: 10810303
Source
Medline
License
Unknown

Abstract

The thyromimetic compound SK&F L-94901 shows more potent thyromimetic activity in the liver than in the pituitary gland or heart when administered to rats. The mechanisms of liver-selectivity of SK&F L-94901 were examined using cultured rat hepatoma cells (dRLH-84) and rat pituitary tumor cells (GH3), both of which showed saturable cellular uptake of tri-iodothyronine (T(3)). When isolated nuclei with partial disruption of the outer nuclear membrane were used, SK&F L-94901 competed for [(125)I]T(3) binding to nuclear receptors almost equally in dRLH-84 and GH3 cells. SK&F L-94901 also did not discriminate thyroid hormone receptors (TR) alpha1 and beta1 in terms of binding affinity and activation of the thyroid hormone responsive element. In intact cells, however, SK&F L-94901 was a more potent inhibitor of nuclear [(125)I]T(3) binding in dRLH-84 cells than in GH3 cells at an early phase of the nuclear uptake process and after binding equilibrium. These data suggest that SK&F L-94901 is more effectively transported to nuclear TRs in hepatic cells than in pituitary cells and therefore shows liver-selective thyromimetic activity. In conclusion, SK&F L-94901 discriminates hepatic cells and pituitary cells at the nuclear transport process. The cellular transporters responsible for this discrimination were not evident.

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