Weak estrogenic activity of phenol red in the pituitary gonadotroph: re-evaluation of estrogen and antiestrogen effects.
Phenol Red (Phr) which is widely used as a pH indicator in cell culture media has recently been described to possess estrogenic activity in different cell types. In the present study we investigated if the dye shows such activity on LH secretion of cultivated rat pituitary cells and controlled the established effects of estradiol (E2) and keoxifene (K) in this model in the absence of Phenol Red. 24 h treatment of pituitary cell cultures with Phr led to enhancement of GnRH-stimulated LH secretion whereas 4 h treatment reduced LH secretion. When the cells received E2 instead of Phr for the indicated incubation periods we observed nearly identical results i.e. a short-term inhibitory and a long-term stimulatory effect on LH secretion. 24 h treatment of pituitary cell cultures with increasing concentrations of Phr led to a stimulatory effect on GnRH-stimulated LH secretion an effect that occurred at 10 microM got maximal at 100 microM and was lost at higher concentrations resulting in a bell-shaped dose-response curve. The inhibitory action of Phr was present at concentrations greater than or equal to 10 microM. Both effects could be blocked by the antiestrogen K indicating their specificity. K has recently been described to induce an antigonadotrophic effect in this model. Although high concentrations of the antiestrogen were still able to inhibit LH secretion this effect was not present at lower concentrations when Phr-free culture medium was used in the experiments. Thus Phr showed weak estrogenic activity in the gonadotroph. The established actions of E2 and K on LH secretion were qualitatively reproducible when Phr was excluded from the culture medium.
Department of Obstetrics and Gynecology, Medical University of Lübeck, F.R.G.
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Ortmann
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Sturm
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Knuppen
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Emons
D000818:Animals; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000494:pharmacology*; D004965:Estrogen Antagonists; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000378:metabolism*; D010635:Phenolphthaleins / Q000494:pharmacology*; D010637:Phenolsulfonphthalein / Q000008:administration & dosage / Q000494:pharmacology*; D010880:Piperidines / Q000008:administration & dosage / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D020849:Raloxifene Hydrochloride; D051381:Rats; D011919:Rats, Inbred Strains
D004965:Estrogen Antagonists; D010635:Phenolphthaleins; D010880:Piperidines; D007987:Gonadotropin-Releasing Hormone; D020849:Raloxifene Hydrochloride; D004958:Estradiol; D007986:Luteinizing Hormone; D010637:Phenolsulfonphthalein