Dean C E, Morpurgo B, Porter T E
Department of Poultry Science, Texas A&M University, College Station, TX, USA.
Endocrine. 1999 Oct;11(2):151-6. doi: 10.1385/ENDO:11:2:151.
Somatotroph differentiation in the embryonic pituitary of avian and mammalian species can be stimulated by glucocorticoids in vitro, and this effect can be augmented by concomitant treatment with growth hormone-releasing hormone (GHRH). Owing to its isolation from maternal influences, the chick embryo is a useful model for studying humoral regulation of pituitary cell differentiation. Somatotroph differentiation in chickens occurs between embryonic day (e-) 14 and e-16, and treatment of e-12 pituitary cells with e-16 serum or corticosterone induces growth hormone (GH) cell differentiation within 2 d in culture. The objective of the present study was to determine whether direct administration of embryonic serum and corticosterone to developing chick embryos was effective in vivo in inducing somatotroph differentiation prematurely. The albumen of fertile eggs was injected on e-11 with 300 approximately microL of 0.9% saline or 150 microL of serum from e-12 or e-16 chick embryos diluted 1:1 with saline. The embryos were allowed to develop until e-14, when pituitaries were dispersed and the resulting pituitary cells were subjected to reverse hemolytic plaque assays (RHPA) and immunocytochemistry to detect GH-secreting and GH-containing cells, respectively. Injection of e-16 serum increased (p < 0.01) GH-secreting and GH-containing cells to 11.5 +/- 1.0% and 1 7.4 +/- 3.3% of all pituitary cells, compared to 5.0 +/- 0.3% and 5.5 +/- 0.9% for saline-injected controls, respectively. Day 12 serum increased GH-containing cells to 9.8 +/- 0.9%, without changing percentages of GH-secreting cells. In experiment 2, saline, e-16 serum, and corticosterone were injected on e-11, and pituitary cells were subjected to GH RHPA on e-14. GH secretors were increased by e-16 serum and corticosterone. In experiment 3, we tested whether GHRH would magnify the effect of corticosterone, as we had seen in extended 6-d cultures previously. Saline, corticosterone, and corticosterone plus GHRH were injected on e-11, and pituitary cells were subjected to GH RHPA on e-18. Treatment with corticosterone alone and combined with GHRH increased the percentage of GH-secreting cells. However, combined treatment with corticosterone and GHRH was not more effective than corticosterone alone. The present findings demonstrate that glucocorticoid administration can stimulate somatotroph differentiation in living vertebrate embryos isolated from maternal interactions.
在体外，糖皮质激素可刺激鸟类和哺乳动物胚胎垂体中的促生长激素细胞分化，生长激素释放激素（GHRH）联合处理可增强这种效应。由于鸡胚不受母体影响，是研究垂体细胞分化体液调节的有用模型。鸡的促生长激素细胞分化发生在胚胎期（e-）14至e-16之间，用e-16血清或皮质酮处理e-12垂体细胞可在培养2天内诱导生长激素（GH）细胞分化。本研究的目的是确定在发育中的鸡胚体内直接注射胚胎血清和皮质酮是否能有效提前诱导促生长激素细胞分化。在e-11时，向受精蛋的蛋白中注射300微升左右的0.9%生理盐水或150微升用生理盐水1:1稀释的e-12或e-16鸡胚血清。让胚胎发育至e-14，此时将垂体分散，对所得垂体细胞分别进行反向溶血空斑试验（RHPA）和免疫细胞化学检测，以检测分泌GH和含GH的细胞。注射e-16血清使分泌GH和含GH的细胞分别增加至所有垂体细胞的11.5±1.0%和17.4±3.3%，而注射生理盐水的对照组分别为5.0±0.3%和5.5±0.9%（p<0.01）。e-12血清使含GH的细胞增加至9.8±0.9%，而分泌GH细胞的百分比未改变。在实验2中，在e-11时注射生理盐水、e-16血清和皮质酮，在e-14时对垂体细胞进行GH RHPA检测。e-16血清和皮质酮使GH分泌细胞增加。在实验3中，我们测试了GHRH是否会像我们之前在延长至6天的培养中看到的那样，放大皮质酮的作用。在e-11时注射生理盐水、皮质酮以及皮质酮加GHRH，在e-18时对垂体细胞进行GH RHPA检测。单独使用皮质酮以及皮质酮与GHRH联合处理均增加了分泌GH细胞的百分比。然而，皮质酮与GHRH联合处理并不比单独使用皮质酮更有效。本研究结果表明，给予糖皮质激素可刺激脱离母体相互作用的活体脊椎动物胚胎中的促生长激素细胞分化。
