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DOI: 10.1055/s-2001-12010
© Georg Thieme Verlag Stuttgart · New York
The Coumarin Osthol Attenuates the Binding of Thyrotropin-Releasing Hormone in Rat Pituitary GH4C1 Cells
Publikationsverlauf
April 13, 2000
October 8, 2000
Publikationsdatum:
31. Dezember 2001 (online)
![](https://www.thieme-connect.de/media/plantamedica/200103/lookinside/thumbnails/10.1055-s-2001-12010-1.jpg)
Abstract
The influence of two plant coumarins, osthol and xanthotoxin, on intracellular Ca2+ ([Ca2+]i) transients evoked by TRH were studied in clonal rat pituitary GH4C1 cells. Osthol, but not xanthotoxin, decreased the TRH-induced transient increase in [Ca2+]i in Fluo-3 loaded cells incubated in Ca2+-free buffer. Binding experiments with [3 H]TRH showed that osthol decreased the binding of TRH to its receptor, whereas the affinity of the receptor for TRH increased. This resulted in a decreased TRH-evoked production of IP3 in cells treated with osthol, and a decreased mobilization of sequestered calcium. Osthol did not inhibit the release of calcium evoked by exogenous IP3 in permeabilized cells. Furthermore, osthol decreased the uptake of 45Ca2+ in response to high K+. Xanthotoxin had no effects in these experiments. The results show that osthol modulates TRH-evoked responses by interacting with the TRH receptor.
Key words
GH4C1 cells - coumarins - thyrotropin-releasing hormone (TRH)
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Prof. Dr. Heikki Vuorela
Department of Pharmacy
Division of Pharmacognosy
P.O. Box 56
00014 University of Helsinki
Finland
eMail: heikki.vuorela@helsinki.fi
Fax: +358 9 191 59 138