Fan G, Rillema J A
Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan 48201.
Proc Soc Exp Biol Med. 1993 Sep;203(4):501-4. doi: 10.3181/00379727-203-43629.
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.
研究了冈田酸对源自妊娠中期小鼠的培养乳腺组织中鸟氨酸脱羧酶（ODC）活性和乳成分形成的影响。冈田酸刺激了ODC活性以及乳糖、脂质和富含酪蛋白的磷蛋白的合成。当共同测试时，冈田酸和催乳素对乳糖合成产生非累加性刺激。此外，冈田酸和催乳素对乳糖合成的作用时间进程相同。与冈田酸和催乳素对乳糖合成的作用相反，这些试剂对ODC活性以及脂质和富含酪蛋白的磷蛋白的合成产生累加性刺激作用。由于已知冈田酸可抑制蛋白磷酸酶-1和2A，我们得出结论，这些磷酸酶的底物参与了催乳素在乳腺组织中表达其对乳糖合成作用的信号转导途径。这些底物是否也参与催乳素在乳腺组织中的其他作用还有待确定。
