A Novel Feedback Mechanism Regulating Growth Hormone Synthesis and Secretion in Chinese Grass Carp (Ctenopharyngodon idellus)

在草魚種新發現的生長激素合成和分泌的反饋調控機理

黃安林(Anderson O. L. Wong) ； 周紅(Hong Zhou) ； 高潔芸(Wendy K. W. Ko) ； 何國強(Walter K. K. Ho)

《臺灣水產學會刊》 31卷2期 (2004/06) Pp. 141-153

https://doi.org/10.29822/JFST.200406.0006

摘要

促性腺激素(GTHⅡ)與生長激素(GH)由腦下垂體前葉所釋放，為調控生殖與成長最重要的激素。此二者激素可在多階層交互作用調整以促性腺與促生長為主軸的重要功能。硬骨魚的腦下垂體細胞的分佈有別於哺乳類的隨機分佈而是有特定區域分佈。在草魚腦下垂體，促生長腺與促性腺完全位於近端遠側垂體(PPT)，是由一叢位在腦下垂體後葉的PPT的神經分泌細胞，延伸至促生長腺基質。這樣的空間分佈提供了此二型細胞間交互作用以自分泌或旁分泌的機制的解剖證據。使用草魚為實驗魚種，我們發現促生長腺與促性腺間有生長激素釋放的迴饋控制。此迴饋控制包含三個成分，分別為(1)GTHⅡ誘導生長激素釋放、(2)生長激素藉由促進生長激素釋放而導致生長激素分泌及(3)生長激素抑制GTHⅡ釋放。促生長腺與促性腺間交互作用透過自分泌或旁分泌而成一區域性迴饋控制GTHⅡ及GH的分泌。本篇文章為第一篇報導有關魚類功能性腦下垂體內迴饋控制而維持生殖與成長。

關鍵字

生長激素 ； 促性腺激素－Ⅱ ； 自分泌／旁分泌 ； 相互作用 ； 促性腺激素細胞 ； 促生長激素細胞 ； 草魚

並列摘要

Gonadotropin-Ⅱ (GTH-Ⅱ) and growth hormone (GH) are the key hormones released from the anterior pituitary regulating reproductive functions and body growth, respectively. These two hormones can interact at multiple levels to modulate the important functions of the gonadotrophic and somatotrophic axes. The bony fish, or teleosts, are unique for the zonal distribution of pituitary cells in the pituitary, which is quite different from the random distribution reported in mammals. In the grass carp pituitary, somatotrophs and gonadotrophs are located exclusively in the proximal pars distalis, with small clusters of gonadotrophs embedding in a matrix of somatotrophs. This spatial relationship provides the anatomical substrate for functional interactions between the two cell types through autocrine/paracrine mechanisms. Using Chinese grass carp as a model, we have recently identified a novel intrapituitary feedback loop regulating GH release by local interactions between somatotrophs and gonadotrophs. This feedback loop has three components, namely (i) GTH-Ⅱ induction of GH release from somatotrophs, (ii) amplification of GH secretion through GH-induced GH release from somatotrophs, and (iii) GH ”feedback inhibition” on GTH-II release in adjacent gonadotrophs. The autocrine/paracrine interactions between the two cell types form a local feedback loop maintaining basal GH and GTH-Ⅱ secretion at the pituitary level. To our knowledge, our study represents the first report of a functional ”intrapituitary circuitry” maintaining body growth and reproductive functions in teleosts.

並列關鍵字

Growth Hormone ； Gonadotropin-Ⅱ ； Autocrine/Paracrine Interactions ； Gonadotrophs ； Somatotrophs ； Chinese Grass Carp