Relationship between [125I]RTI-55-labeled cocaine binding sites and the serotonin transporter in rat placenta

Lauren P. Shearman, Alison M. McReynolds, Feng C. Zhou, Jerrold S. Meyer

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

We investigated the characteristics of cocainelike binding sites in rat placenta using [125I]RTI-55. [3H]paroxetine binding and immunocytochemical staining for serotonin [5-hydroxytryptamine (5-HT)] and for the 5-HT transporter were also used to obtain evidence for rat placenta] 5-HT uptake. [125I]RTI-55 saturation analyses with membranes from normal gestational day 20 placentas yielded curvilinear Scatchard plots that were resolved into high- and low-affinity components (mean dissociation constants of 0.29 and 7.9 nM, respectively). Drug competition studies with various monoamine uptake inhibitors gave rise to complex multiphasic displacement curves, although the results obtained with the selective 5-HT uptake inhibitor citalopram suggest that the 5-HT transporter is an important component of placental high-affinity [125I]RTI-55 binding. The presence of a rat placental 5-HT uptake system was additionally supported by the [3H]paroxetine binding experiments and by the presence throughout the placenta of immunoreactivity for 5-HT and the 5-HT transporter. Immunostaining with both antibodies was most intense in the junctional zone, whereas the density of [125I]RTI-55 binding sites was greater in the placental labyrinth. This discrepancy may be due to the fact that [125I]RTI-55 appears to be labeling additional cellular components besides the 5-HT transporter. The presence of cocaine- and antidepressant-sensitive 5-HT transporters in the placenta has important implications for the possible effects of these compounds on pregnancy and fetal development.

Original languageEnglish (US)
Pages (from-to)C1621-C1629
JournalAmerican Journal of Physiology - Cell Physiology
Volume275
Issue number6 44-6
StatePublished - Dec 1 1998

Fingerprint

Serotonin Plasma Membrane Transport Proteins
Cocaine
Placenta
Rats
Serotonin
Binding Sites
Paroxetine
RTI 55
Citalopram
Serotonin Uptake Inhibitors
Inner Ear
Fetal Development
Labeling
Antidepressive Agents
Staining and Labeling
Membranes
Pregnancy

Keywords

  • Development
  • Immunocytochemistry
  • Paroxetine
  • Uptake

ASJC Scopus subject areas

  • Clinical Biochemistry
  • Cell Biology
  • Physiology
  • Physiology (medical)

Cite this

Relationship between [125I]RTI-55-labeled cocaine binding sites and the serotonin transporter in rat placenta. / Shearman, Lauren P.; McReynolds, Alison M.; Zhou, Feng C.; Meyer, Jerrold S.

In: American Journal of Physiology - Cell Physiology, Vol. 275, No. 6 44-6, 01.12.1998, p. C1621-C1629.

Research output: Contribution to journalArticle

Shearman, Lauren P. ; McReynolds, Alison M. ; Zhou, Feng C. ; Meyer, Jerrold S. / Relationship between [125I]RTI-55-labeled cocaine binding sites and the serotonin transporter in rat placenta. In: American Journal of Physiology - Cell Physiology. 1998 ; Vol. 275, No. 6 44-6. pp. C1621-C1629.
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