Waters S B, Rillema J A
Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan 48201.
Am J Physiol. 1988 Oct;255(4 Pt 1):E567-71. doi: 10.1152/ajpendo.1988.255.4.E567.
Prolactin (PRL) stimulates an increased rate of incorporation of [14C]acetate and [3H]glucose into lipids in cultured mammary gland explants from 10- to 14-day-pregnant mice. This response is biphasic with an early increase occurring from 6 through 12 h, and an additional increase from 16 through 24 h. Enzymes likely to be rate limiting to this process include acetyl CoA carboxylase, fatty acid synthetase, acetyl CoA synthetase, and/or pyruvate dehydrogenase. Of these enzymes only pyruvate dehydrogenase activity was elevated at 6 h, suggesting that this enzymatic activity is important in stimulating early increases in lipogenesis after PRL treatment. In addition, the PRL stimulation of pyruvate dehydrogenase may also indirectly stimulate acetyl CoA carboxylase through the generation of citrate; this may explain the early (6-12 h) effect of PRL on [14C]acetate incorporation. After 16 h of PRL treatment, the activities of all the lipogenic enzymes were enhanced. The second phase of PRLs stimulation of lipogenesis thus likely involves the enhanced activities of more than one of the lipogenic enzymes.
催乳素（PRL）可刺激来自怀孕10至14天小鼠的培养乳腺外植体中，[14C]乙酸盐和[3H]葡萄糖掺入脂质的速率增加。这种反应是双相的，早期增加发生在6至12小时，另外在16至24小时出现额外增加。可能对此过程起限速作用的酶包括乙酰辅酶A羧化酶、脂肪酸合成酶、乙酰辅酶A合成酶和/或丙酮酸脱氢酶。在这些酶中，只有丙酮酸脱氢酶活性在6小时时升高，这表明该酶活性在刺激PRL处理后脂肪生成的早期增加中很重要。此外，PRL对丙酮酸脱氢酶的刺激也可能通过柠檬酸的生成间接刺激乙酰辅酶A羧化酶；这可能解释了PRL对[14C]乙酸盐掺入的早期（6 - 12小时）效应。PRL处理16小时后，所有脂肪生成酶的活性均增强。因此，PRL刺激脂肪生成的第二阶段可能涉及多种脂肪生成酶活性的增强。
