Kühn E R, Decuypere E, Hemschoote K, Berghman L, Paulussen J
J Endocrinol. 1983 Dec;99(3):401-7. doi: 10.1677/joe.0.0990401.
The influence of an intravenous injection of ovine prolactin on circulating levels of thyroid hormones was studied in Rhode Island Red embryos and chicks after hatching. In the chick embryo, 2 h after injection of 0.1 microgram prolactin (on incubation day 19), serum triiodothyronine (T3) increased threefold; after 10 or 100 micrograms prolactin (on incubation day 18) serum T3 increased 15- to 25-fold. These profound increases were not observed in chicks after hatching. Serum concentrations and thyroid content of thyroxine (T4) in embryos and chicks of all ages studied were not influenced by the prolactin injections. Maximal serum concentrations of reverse T3 (rT3) were found on incubation day 18 (110.25 +/- 23.36 pmol/l; 71.66 +/- 15.18 pg/ml; n = 8), whereas after hatching no rT3 could be detected. An injection of 10 micrograms prolactin on day 18 depressed serum rT3 after 2 h to 5.68 +/- 3.20 pmol/l (3.69 +/- 2.08 pg/ml; n = 8; P less than 0.001); the effect of 100 micrograms prolactin was less pronounced. After hatching, chronic administration of prolactin resulted in decreased serum levels of T3, but not of T4, and hypertrophy of the follicles in the thyroid gland. It is concluded that prolactin plays a major role in the maturation of embryonic thyroid metabolism by changing the T4-5-monodeiodination into a T4-5'-monodeiodination. The hypertrophy of the thyroid gland observed after hatching following prolonged prolactin administration may be due to decreased negative feedback of T3 on the hypophysis.
研究了静脉注射绵羊催乳素对罗德岛红鸡胚胎及孵化后雏鸡甲状腺激素循环水平的影响。在鸡胚胎中，注射0.1微克催乳素（孵化第19天）2小时后，血清三碘甲状腺原氨酸（T3）增加了两倍；注射10或100微克催乳素（孵化第18天）后，血清T3增加了15至25倍。在孵化后的雏鸡中未观察到这些显著增加。所研究的所有年龄段胚胎和雏鸡的血清甲状腺素（T4）浓度及甲状腺含量均不受催乳素注射的影响。在孵化第18天发现反式T3（rT3）的最大血清浓度（110.25±23.36 pmol/l；71.66±15.18 pg/ml；n = 8），而孵化后未检测到rT3。在第18天注射10微克催乳素2小时后，血清rT3降至5.68±3.20 pmol/l（3.69±2.08 pg/ml；n = 8；P＜0.001）；100微克催乳素的作用不太明显。孵化后，长期给予催乳素导致血清T3水平降低，但T4水平未降低，且甲状腺滤泡肥大。结论是，催乳素通过将T4 - 5 - 单脱碘转变为T4 - 5'- 单脱碘，在胚胎甲状腺代谢成熟中起主要作用。孵化后长期给予催乳素后观察到的甲状腺肥大可能是由于T3对垂体的负反馈减少所致。
