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首页> 外文期刊>Life sciences >Direct effects of growth hormone (GH)-releasing hexapeptide (GHRP-6) and GH-releasing factor (GRF) on GH secretion from cultured porcine somatotropes.
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Direct effects of growth hormone (GH)-releasing hexapeptide (GHRP-6) and GH-releasing factor (GRF) on GH secretion from cultured porcine somatotropes.

机译：生长激素（GH）释放六肽（GHRP-6）和GH释放因子（GRF）对培养的猪生长激素生长激素分泌的直接影响。

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摘要

Growth hormone (GH)-releasing hexapeptide (GHRP-6) belongs to the expanding family of synthetic GH secretagogues (GHSs). Previous studies have shown that non-peptidyl GHRP-6 analogues stimulate GH release in vivo in pigs, and interact synergistically with GH-releasing factor (GRF), but its direct effects on porcine somatotropes have not been addressed hitherto. In the present study, we have evaluated the response of cultured porcine pituitary cells to GHRP-6, and its interaction with GRF and somatostatin (SRIF). Secretory response of somatotropes was assessed by using two distinct techniques. GH released by monolayer cell cultures was evaluated by enzyme immunoassay, whereas that secreted by individual somatotropes was measured by immunodensitometry using a cell blotting assay. Our results demonstrate that both GHRP-6 and GRF stimulated GH release from monolayer cultures at doses equal to or above 10(-9) M. Use of cell immunoblot assay demonstrated that, like GRF, the hexapeptide acts directly upon porcine somatotropes to exert its action. Moreover, regardless of the technique applied, combined administration of GHRP-6 (10(-6) or 10(-9) M) and GRF (10(-8) M) resulted in an additive, but not synergistic, stimulatory GH response. Finally, SRIF (10(-7) M) inhibited the stimulatory effect of GHRP-6 alone or in combination with GRF. These results indicate that GHRP-6 directly and effectively stimulates GH secretion from porcine somatotropes in vitro, and acts additively when coadministered with GRF. Therefore, the synergistic stimulatory effect of GHSs and GRF reported in vivo in this species might require additional factors that are lacking in the in vitro situation.
机译：释放生长激素（GH）的六肽（GHRP-6）属于合成GH促分泌素（GHS）的扩展家族。先前的研究表明，非肽基GHRP-6类似物可刺激猪体内的GH释放，并与GH释放因子（GRF）协同作用，但迄今尚未解决其对猪生长激素的直接作用。在本研究中，我们评估了培养的猪垂体细胞对GHRP-6的反应及其与GRF和生长抑素（SRIF）的相互作用。通过使用两种不同的技术评估了促生长素的分泌反应。通过酶免疫测定法评估单层细胞培养物释放的GH，而使用细胞印迹法通过免疫密度测定法测量各个生长激素分泌的GH。我们的结果表明，GHRP-6和GRF均以等于或高于10（-9）M的剂量刺激了单层培养物中的GH释放。使用细胞免疫印迹分析表明，六肽与GRF一样，直接作用于猪生长激素，以发挥其作用。行动。此外，无论采用何种技术，GHRP-6（10（-6）或10（-9）M）和GRF（10（-8）M）的联合给药均会产生加性反应，但不会产生刺激性GH反应。最后，SRIF（10（-7）M）单独或与GRF联合抑制GHRP-6的刺激作用。这些结果表明，GHRP-6在体外直接有效地刺激猪生长激素的GH分泌，并且在与GRF共同施用时起相加作用。因此，在该物种体内报道的GHS和GRF的协同刺激作用可能需要体外条件下缺少的其他因素。

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