Effects of the protein phosphatase inhibitor okadaic acid on the actions of prolactin in cultured mouse mammary gland explants

Guang Fan, J. A. Rillema

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

The effects of okadaic acid on ornithine decarboxylase (ODC) activity and milk product formation were studied in cultured mammary tissues derived from midpregnant mice. Okadaic acid stimulated ODC activity as well as the synthesis of lactose, lipids, and casein-rich phosphoproteins. When tested together, okadaic acid and prolactin evoked a nonadditive stimulation of lactose synthesis. In addition, the time-courses for the okadaic acid and prolactin effects on lactose synthesis were the same. In contrast to the effects of okadaic acid and prolactin on lactose synthesis, these agents generated additive stimulatory effects on ODC activity and the synthesis of lipids and casein-rich phosphoproteins. Since okadaic acid is known to inhibit protein phosphatases-1 and 2A, we conclude that the substrate(s) of these phosphatases are involved in the signal transduction pathway by which prolactin expresses its effect on lactose synthesis in mammary tissues. Whether these substrates are also involved in other actions of prolactin in mammary tissues remains to be established.

Original languageEnglish (US)
Pages (from-to)501-504
Number of pages4
JournalProceedings of the Society for Experimental Biology and Medicine
Volume203
Issue number4
StatePublished - 1993
Externally publishedYes

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Okadaic Acid
Phosphoprotein Phosphatases
Human Mammary Glands
Prolactin
Lactose
Ornithine Decarboxylase
Breast
Phosphoproteins
Tissue
Caseins
Lipids
Protein Phosphatase 1
Protein Phosphatase 2
Signal transduction
Substrates
Phosphoric Monoester Hydrolases
Signal Transduction
Milk

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)

Cite this

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abstract = "The effects of okadaic acid on ornithine decarboxylase (ODC) activity and milk product formation were studied in cultured mammary tissues derived from midpregnant mice. Okadaic acid stimulated ODC activity as well as the synthesis of lactose, lipids, and casein-rich phosphoproteins. When tested together, okadaic acid and prolactin evoked a nonadditive stimulation of lactose synthesis. In addition, the time-courses for the okadaic acid and prolactin effects on lactose synthesis were the same. In contrast to the effects of okadaic acid and prolactin on lactose synthesis, these agents generated additive stimulatory effects on ODC activity and the synthesis of lipids and casein-rich phosphoproteins. Since okadaic acid is known to inhibit protein phosphatases-1 and 2A, we conclude that the substrate(s) of these phosphatases are involved in the signal transduction pathway by which prolactin expresses its effect on lactose synthesis in mammary tissues. Whether these substrates are also involved in other actions of prolactin in mammary tissues remains to be established.",
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N2 - The effects of okadaic acid on ornithine decarboxylase (ODC) activity and milk product formation were studied in cultured mammary tissues derived from midpregnant mice. Okadaic acid stimulated ODC activity as well as the synthesis of lactose, lipids, and casein-rich phosphoproteins. When tested together, okadaic acid and prolactin evoked a nonadditive stimulation of lactose synthesis. In addition, the time-courses for the okadaic acid and prolactin effects on lactose synthesis were the same. In contrast to the effects of okadaic acid and prolactin on lactose synthesis, these agents generated additive stimulatory effects on ODC activity and the synthesis of lipids and casein-rich phosphoproteins. Since okadaic acid is known to inhibit protein phosphatases-1 and 2A, we conclude that the substrate(s) of these phosphatases are involved in the signal transduction pathway by which prolactin expresses its effect on lactose synthesis in mammary tissues. Whether these substrates are also involved in other actions of prolactin in mammary tissues remains to be established.

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