Regulation of dopamine D2 receptors in a novel cell line (SUP1)

K. J. Ivins, R. R. Luedtke, R. P. Artymyshyn, P. B. Molinoff

Research output: Contribution to journalArticle

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Abstract

A prolactin-secreting cell line, SUP1, has been established from rat pituitary tumor 7315a. In radioligand binding experiments, the D2 receptor antagonist (S)-(-)-3-[125I]iodo-2-hydroxy-6-methoxy-N-[(1-ethyl-2- pyrrolidinyl)methyl]benzamide ([125I]IBZM) labeled a single class of sites in homogenates of SUP1 cells (K(d) = 0.6 nM; B(max) = 45 fmol/mg of protein). The sites displayed a pharmacological profile consistent with that of D2 receptors. Inhibition of the binding of [125I]IBZM by dopamine was sensitive to GTP, suggesting that D2 receptors in SUP1 cells are coupled to guanine nucleotide-binding protein(s). In the presence of isobutylmethylxanthine, dopamine decreased the level of cAMP accumulation in SUP1 cells. Dopamine also inhibited prolactin secretion from SUP1 cells. Both the inhibition of cAMP accumulation and the inhibition of prolactin secretion were blocked by D2 receptor antagonists, suggesting that these effects of dopamine were mediated by an interaction with D2 receptors. The regulation of D2 receptors in SUP1 cells by D2 receptor agonists was investigated. Exposure of SUP1 cells to dopamine or to the D2 receptor agonist N-propylnorapomorphine led to increased expression of D2 receptors, with no change in the affinity of the receptors for [125I]IBZM. An increase in the density of D2 receptors in SUP1 cells was evident within 7 hr of exposure to dopamine. Spiroperidol, a D2 receptor antagonist, blocked the effect of dopamine on receptor density. These results suggest that exposure of D2 receptors in SUP1 cells to agonists leads to an up-regulation of D2 receptors. Dopamine retained the ability to inhibit cAMP accumulation in SUP1 cells exposed to dopamine for 24 hr, suggesting that D2 receptors in SUP1 cells are not desensitized by prolonged exposure to agonist. SUP1 cells should be a useful model system for future studies of the regulation of the expression and function of D2 receptors in cultured cells.

Original languageEnglish
Pages (from-to)531-539
Number of pages9
JournalMolecular Pharmacology
Volume39
Issue number4
StatePublished - 30 May 1991

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Dopamine D2 Receptors
Cell Line
Dopamine
Prolactin
Spiperone
Guanine Nucleotides
Dopamine Receptors
Pituitary Neoplasms
Guanosine Triphosphate
Cultured Cells
Carrier Proteins
Up-Regulation
Pharmacology

Cite this

Ivins, K. J., Luedtke, R. R., Artymyshyn, R. P., & Molinoff, P. B. (1991). Regulation of dopamine D2 receptors in a novel cell line (SUP1). Molecular Pharmacology, 39(4), 531-539.
Ivins, K. J. ; Luedtke, R. R. ; Artymyshyn, R. P. ; Molinoff, P. B. / Regulation of dopamine D2 receptors in a novel cell line (SUP1). In: Molecular Pharmacology. 1991 ; Vol. 39, No. 4. pp. 531-539.
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abstract = "A prolactin-secreting cell line, SUP1, has been established from rat pituitary tumor 7315a. In radioligand binding experiments, the D2 receptor antagonist (S)-(-)-3-[125I]iodo-2-hydroxy-6-methoxy-N-[(1-ethyl-2- pyrrolidinyl)methyl]benzamide ([125I]IBZM) labeled a single class of sites in homogenates of SUP1 cells (K(d) = 0.6 nM; B(max) = 45 fmol/mg of protein). The sites displayed a pharmacological profile consistent with that of D2 receptors. Inhibition of the binding of [125I]IBZM by dopamine was sensitive to GTP, suggesting that D2 receptors in SUP1 cells are coupled to guanine nucleotide-binding protein(s). In the presence of isobutylmethylxanthine, dopamine decreased the level of cAMP accumulation in SUP1 cells. Dopamine also inhibited prolactin secretion from SUP1 cells. Both the inhibition of cAMP accumulation and the inhibition of prolactin secretion were blocked by D2 receptor antagonists, suggesting that these effects of dopamine were mediated by an interaction with D2 receptors. The regulation of D2 receptors in SUP1 cells by D2 receptor agonists was investigated. Exposure of SUP1 cells to dopamine or to the D2 receptor agonist N-propylnorapomorphine led to increased expression of D2 receptors, with no change in the affinity of the receptors for [125I]IBZM. An increase in the density of D2 receptors in SUP1 cells was evident within 7 hr of exposure to dopamine. Spiroperidol, a D2 receptor antagonist, blocked the effect of dopamine on receptor density. These results suggest that exposure of D2 receptors in SUP1 cells to agonists leads to an up-regulation of D2 receptors. Dopamine retained the ability to inhibit cAMP accumulation in SUP1 cells exposed to dopamine for 24 hr, suggesting that D2 receptors in SUP1 cells are not desensitized by prolonged exposure to agonist. SUP1 cells should be a useful model system for future studies of the regulation of the expression and function of D2 receptors in cultured cells.",
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Ivins, KJ, Luedtke, RR, Artymyshyn, RP & Molinoff, PB 1991, 'Regulation of dopamine D2 receptors in a novel cell line (SUP1)', Molecular Pharmacology, vol. 39, no. 4, pp. 531-539.

Regulation of dopamine D2 receptors in a novel cell line (SUP1). / Ivins, K. J.; Luedtke, R. R.; Artymyshyn, R. P.; Molinoff, P. B.

In: Molecular Pharmacology, Vol. 39, No. 4, 30.05.1991, p. 531-539.

Research output: Contribution to journalArticle

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Ivins KJ, Luedtke RR, Artymyshyn RP, Molinoff PB. Regulation of dopamine D2 receptors in a novel cell line (SUP1). Molecular Pharmacology. 1991 May 30;39(4):531-539.