Strbák V, Jurcovicová J, Vigas M
Endocrinol Exp. 1981 Dec;15(4):245-9.
Small doses of TRH elicit GH release from rat pituitary provided the pituitary lacks CNS influences (e.g. in vitro or in ectopic pituitaries). We have found previously that hypothalamic regulation of TSH secretion matures between the 5th and 12th postnatal day. Therefore the possibility of TRH induced GH release was investigated in neonatal rats. GH concentration was measured by RIA at 10 min after s.c. TRH administration (4.1 pmol g-1 BW) into female Wistar rats at the age 3, 9, 12, 15, 21, 30 and 100 days. Control animals were injected the same volume (1 microliter g-1 BW) of saline. Serum GH in saline treated animals gradually decreased during postnatal ontogenesis. The TRH induced increase of serum GH level decreased during maturation: the most marked response was found at 3 days, it was somewhat lessened but still significant at 9 days and was absent in 12, 15, 30 days old and adult animals. Surprisingly, in 21 days old animals the increase of GH after TRH administration was again present. We conclude that the ability of TRH to elicit GH release in newborn rats may depend on the maturity of the hypothalamo-pituitary axis. The effect of hypothalamic somatostatin is likely to inhibit such a response at the pituitary level in older rats.
小剂量促甲状腺激素释放激素（TRH）可引起大鼠垂体释放生长激素（GH），前提是垂体不受中枢神经系统影响（如在体外或异位垂体中）。我们之前发现，促甲状腺激素（TSH）分泌的下丘脑调节在出生后第5天至第12天之间成熟。因此，我们研究了新生大鼠中TRH诱导GH释放的可能性。将TRH（4.1 pmol g-1体重）皮下注射到3、9、12、15、21、30和100日龄的雌性Wistar大鼠体内，10分钟后通过放射免疫分析（RIA）测定GH浓度。对照动物注射相同体积（1微升 g-1体重）的生理盐水。生理盐水处理动物的血清GH在出生后的个体发育过程中逐渐下降。TRH诱导的血清GH水平升高在成熟过程中降低：在3天时发现最明显的反应，在9天时有所减弱但仍显著，在12、15、30日龄和成年动物中则无此反应。令人惊讶的是，在21日龄动物中，TRH给药后GH再次升高。我们得出结论，TRH在新生大鼠中引发GH释放的能力可能取决于下丘脑-垂体轴的成熟度。下丘脑生长抑素的作用可能在老年大鼠的垂体水平抑制这种反应。
