Growth hormone-releasing factor increases somatostatin release and mRNA levels in the rat periventricular nucleus via nitric oxide by activation of guanylate cyclase.
Growth hormone-releasing factor increases somatostatin release and mRNA levels in the rat periventricular nucleus via nitric oxide by activation of guanylate cyclase.
复制标题
生长激素释放因子通过激活鸟苷酸环化酶，通过一氧化氮增加大鼠室周核中生长抑素的释放和 mRNA 水平。
DOI：
10.1073/pnas.91.2.782
复制
发表时间：
1994
影响因子：
11.1
通讯作者：
Aguila,MC
中科院分区：
文献类型：
--
作者：
Aguila,MC
以前的工作表明，生长激素释放因子（GRF）刺激cGMP的生产和生长抑素[生长激素（生长激素）释放抑制因子，SRIF]释放，而不改变环腺苷酸积累的片段中隆起在体外孵育。因此，本研究在体外研究GRF和cGMP对雄性大鼠室周核SRIF mRNA和SRIF释放的影响。在存在各种物质的情况下，在Waymouth培养基中孵育6小时的室周核外植体中测定SRIF mRNA水平。使用32 P标记的大鼠SRIF RNA探针，通过S1核酸酶保护试验测量SRIF mRNA的稳态水平。通过RIA在30 min和6 h测量SRIF释放和cGMP形成。SRIF mRNA水平和SRIF释放被1 μ M二丁酰cGMP显著（P < 0.025）增加（约2倍），而丁酸钠没有影响。这种增强不受放线菌酮，蛋白质合成的抑制剂。硝普钠（10 μ M）是鸟苷酸环化酶途径的激活剂，通过其释放一氧化氮，增加（P < 0.001）SRIF mRNA水平并显著增加（P < 0.05）SRIF释放。GRF（1 nM）可增加SRIF mRNA的表达（P < 0.001），并在30 min（P < 0.05）和6 h（P < 0.01）刺激SRIF的释放。这种刺激被10 μ M的NG-单甲基-L-精氨酸（L-NMMA）（一氧化氮合酶的特异性抑制剂）消除，但不被NG-单甲基-D-精氨酸（D-NMMA，无活性异构体）消除。GRF还增加cGMP的形成。这种作用被L-NMMA而不是D-NMMA孵育完全阻断。这些结果表明，GRF释放一氧化氮。一氧化氮扩散到邻近的SRIF神经元，激活鸟苷酸环化酶，导致环鸟苷酸的形成增加。这种cGMP增加雄性大鼠室周核中SRIF mRNA和SRIF释放。
Previous work has shown that growth hormone-releasing factor (GRF) stimulates cGMP production and somatostatin [somatotropin (growth hormone)-release-inhibiting factor, SRIF] release without altering cAMP accumulation by fragments of median eminence incubated in vitro. Therefore, this study was undertaken to evaluate the effect of GRF and cGMP on SRIF mRNA and SRIF release in the periventricular nuclei of male rats in vitro. SRIF mRNA levels were determined in explants of periventricular nuclei incubated for 6 hr in Waymouth's medium in the presence of various substances. Steady-state levels of SRIF mRNA were measured by an S1 nuclease protection assay using a 32P-labeled rat SRIF RNA probe. SRIF release and cGMP formation were measured at 30 min and 6 hr by RIA. SRIF mRNA levels and SRIF release were significantly (P < 0.025) increased (approximately 2-fold) by 1 microM dibutyryl cGMP, whereas sodium butyrate had no effect. This augmentation was not influenced by cycloheximide, an inhibitor of protein synthesis. Sodium nitroprusside (10 microM), an activator of the guanylate cyclase pathway via its release of nitric oxide, augmented (P < 0.001) SRIF mRNA levels and significantly increased (P < 0.05) SRIF release. GRF (1 nM) increased SRIF mRNA (P < 0.001) and stimulated the release of SRIF at 30 min (P < 0.05) and 6 hr (P < 0.01). This stimulation was abolished by 10 microM NG-monomethyl-L-arginine (L-NMMA), a specific inhibitor of nitric oxide synthase, but not by NG-monomethyl-D-arginine (D-NMMA, the inactive isomer). GRF also increased cGMP formation. This effect was completely blocked by incubation with L-NMMA but not D-NMMA. These results indicate that GRF releases nitric oxide. The nitric oxide diffuses to the adjacent SRIF neurons, where it activates guanylate cyclase, leading to increased formation of cGMP. This cGMP increases SRIF mRNA and SRIF release in the periventricular nuclei of male rats.