Bicknell R J, Schofield J G
Mol Cell Endocrinol. 1981 Apr;22(1):85-94. doi: 10.1016/0303-7207(81)90104-0.
The effects of somatostatin on GH secretion, cyclic AMP and cyclic GMp concentrations in dispersed bovine anterior pituitary cells were studied following activation of adenylate cyclase with cholera toxin and inhibition of phosphodiesterase with isobutylmethylxanthine (IBMX). Cholera toxin (10(-5)M) increased intracellular cyclic AMP concentration 10-fold and cyclic GMP concentration 3-fold relative to control, and stimulated the secretion of GH. IBMX (10(-4) M) als increased intracellular concentrations of both cyclic AMP and cyclic GMP and the secretion of GH and potentiated the actions of cholera toxin particularly in raising intracellular cyclic AMP concentrations which were elevated 40-fold in the presence of cholera toxin and IBMX. Somatostatin (5 X 10(-7) M) completely prevented GH secretion elicited by cholera toxin and/or IBMX. Somatostatin was without effect on control cyclic AMP and cyclic GMp concentrations and on the increases in both cyclic AMP and cyclic GMP caused by cholera toxin and by IBMX alone, or in combination. The data suggest that bovine GH secretion is increased when concentrations of either or both cyclic nucleotides are elevated within the cells, although incubation of cells with extracellular concentrations of cyclic AMP and cyclic GMP derivatives up to 2 x 10(-3) M caused only small changes in GH release. We suggest that somatostatin inhibits cholera toxin-induced bovine GH secretion by preventing activation of the secretory process by either cyclic AMP or cyclic GMP.
利用霍乱毒素激活腺苷酸环化酶以及用异丁基甲基黄嘌呤（IBMX）抑制磷酸二酯酶，研究了生长抑素对分散的牛垂体前叶细胞中生长激素（GH）分泌、环磷酸腺苷（cAMP）和环磷酸鸟苷（cGMP）浓度的影响。相对于对照，霍乱毒素（10⁻⁵M）使细胞内cAMP浓度增加了10倍，cGMP浓度增加了3倍，并刺激了GH的分泌。IBMX（10⁻⁴M）也增加了细胞内cAMP和cGMP的浓度以及GH的分泌，并增强了霍乱毒素的作用，特别是在提高细胞内cAMP浓度方面，在霍乱毒素和IBMX共同作用下，cAMP浓度升高了40倍。生长抑素（5×10⁻⁷M）完全抑制了霍乱毒素和/或IBMX引发的GH分泌。生长抑素对对照的cAMP和cGMP浓度以及由霍乱毒素单独或与IBMX联合引起的cAMP和cGMP的增加均无影响。数据表明，当细胞内环核苷酸中的一种或两种浓度升高时，牛GH分泌增加，尽管用高达2×10⁻³M的细胞外cAMP和cGMP衍生物孵育细胞仅引起GH释放的微小变化。我们认为，生长抑素通过阻止cAMP或cGMP激活分泌过程来抑制霍乱毒素诱导的牛GH分泌。
