Hashizume Tsutomu, Horiuchi Mami, Tate Naomi, Nonaka Sumie, Kojima Masayasu, Hosoda Hiroshi, Kangawa Kenji
Faculty of Agriculture, Iwate University, Ueda 3, Morioka 020-8550, Japan.
Endocr J. 2003 Jun;50(3):289-95. doi: 10.1507/endocrj.50.289.
To clarify the direct effects of ghrelin on growth hormone (GH) release from anterior pituitary (AP) cells in cattle, GH-releasing effects of human ghrelin (hGhrelin) and rat ghrelin (rGhrelin) on bovine AP cells were compared with those of GH-releasing hormone (GHRH) in vitro. The AP cells were obtained from Holstein steers and were incubated for 2 h with the peptides after incubating in DMEM for 3 days. hGhrelin and rGhrelin significantly stimulated GH release from the cultured cells at doses from 10(-10) to 10(-7) M and from 10(-9) to 10(-7) M, respectively (P<0.05). The rates of increase in GH at 10(-10), 10(-9), 10(-8) and 10(-7) M hGhrelin were 26, 26, 59 and 100% compared with controls, respectively, and those of increase in GH at 10(-9), 10(-8) and 10(-7) M rGhrelin were 58, 74 and 106%, respectively. GHRH significantly increased GH concentrations in cultured media at a dose as low as 10(-13) M compared with the control (P<0.05). When hGhrelin (10(-8) M) and GHRH (10(-8) M) were added together, the release of GH induced by both peptides was significantly greater than that by hGhrelin alone (P<0.05), and tended to be greater than that by GHRH alone. Somatostatin (SS, 10(-7) M) significantly blunted GH release induced by hGhrelin (10(-8) M) and GHRH (10(-8) M) (P<0.05). In the presence of SS, the percent increase in GH released with hGhrelin plus GHRH was 42% and 14% greater than that by either hGhrelin or GHRH alone, respectively (P<0.05). These results show that ghrelin directly stimulates the release of GH from anterior pituitary cells, and that SS modifies ghrelin-stimulated GH release in cattle.
为阐明胃饥饿素对牛垂体前叶（AP）细胞生长激素（GH）释放的直接影响，在体外比较了人胃饥饿素（hGhrelin）和大鼠胃饥饿素（rGhrelin）与生长激素释放激素（GHRH）对牛AP细胞的GH释放作用。AP细胞取自荷斯坦公牛，在DMEM中培养3天后，再与这些肽一起孵育2小时。hGhrelin和rGhrelin分别在10(-10)至10(-7)M和10(-9)至10(-7)M的剂量下显著刺激培养细胞释放GH（P<0.05）。与对照组相比，10(-10)、10(-9)、10(-8)和10(-7)M hGhrelin刺激GH增加的速率分别为26%、26%、59%和100%，10(-9)、10(-8)和10(-7)M rGhrelin刺激GH增加的速率分别为58%、74%和106%。与对照组相比，GHRH在低至10(-13)M的剂量下就能显著增加培养基中GH的浓度（P<0.05）。当hGhrelin（10(-8)M）和GHRH（10(-8)M）一起添加时，两种肽诱导的GH释放显著大于单独使用hGhrelin时的释放量（P<0.05），且有大于单独使用GHRH时释放量的趋势。生长抑素（SS，10(-7)M）显著抑制hGhrelin（10(-8)M）和GHRH（10(-8)M）诱导的GH释放（P<0.05）。在存在SS的情况下，hGhrelin加GHRH释放的GH增加百分比分别比单独使用hGhrelin或GHRH时高42%和14%（P<0.05）。这些结果表明，胃饥饿素直接刺激垂体前叶细胞释放GH，且SS调节牛体内胃饥饿素刺激的GH释放。
