Cyclic nucleotide metabolism in pineal homogenates.
Cyclic nucleotide metabolism in pineal homogenates.
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松果体匀浆中的环核苷酸代谢。
DOI：
10.1111/j.1600-079x.1988.tb00882.x
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发表时间：
1988
影响因子：
10.3
通讯作者：
Jewell,LS
中科院分区：
文献类型：
--
作者：
Sweat,FW;Carmack,CF;Jewell,LS
用L-去甲肾上腺素（NE）和L-异丙肾上腺素（ISO）刺激家兔、大鼠、牛和田鼠松果体部分中的腺苷酸环化酶（AC）。NE对兔和牛松果体AC的刺激是双相的，在0.01 μM和1.0 μM之间有一个平台，高于1.0 μM的NE有额外的刺激。不同浓度的ISO对AC的刺激呈典型的双曲线型，ISO的最佳刺激作用大于NE，褪黑素使AC的ISO和NE刺激作用降低10- 20%。尽管α肾上腺素能激动剂增加β激动剂介导的完整松果体细胞中腺苷-3 ′，5′-环磷酸（cAMP）的积累，但在破碎细胞制备物中未观察到类似的AC刺激放大。在110，000 × g离心匀浆后，大多数（60-70%）松果体鸟苷酸环化酶（GC）在上清液中回收;这种可溶性GC不受潜在激动剂的影响。低浓度（0.01-1 nM）的NE、ISO和苯丙氨酸（PE）在不纯和纯化的膜组分中刺激GC，但在浓度高于10 μM时均抑制GC。在存在α-激动剂PE的情况下，所有浓度的ISO和NE均抑制GC。单独的褪黑激素不影响颗粒GC，但在相同浓度的褪黑激素存在下，没有观察到L-ISO刺激。体外数据与松果体细胞中环核苷酸代谢的α和β受体调节一致。内源性NE可能对松果体中的环磷酸腺苷和环磷酸鸟苷（cGMP）有不同的调节作用;低浓度的NE刺激GC对AC只有轻微的影响，但高浓度的NE抑制GC最大程度地刺激AC。颗粒GC和AC也通过平衡离心分离，得到几个离散的酶活性峰。结果支持存在几种形式的AC和GC，它们对肾上腺素能激动剂有不同的反应。
Adenylate cyclase (AC) in pineal paniculate fractions from rabbit, rat, cow, and the voleMicrotus montanuswas stimulated by L‐norepinephrine (NE) and L‐isopro‐terenol (ISO). NE stimulation of rabbit and bovine pineal AC was biphasic, with a plateau between 0.01 μM and 1.0 μM and additional stimulation by NE above 1.0 μM. Stimulation by different ISO concentrations gave a typical hyperbolic curve, and optimal stimulation by ISO exceeded that by NE.Melatonin decreased ISO and NE stimulation of AC 10–20%. Although α‐ad‐renergic agonists increase β‐agonist‐mediated adenosine‐3′, 5′‐cyclic monophosphate (cyclic AMP) accumulation in intact pinealocytes, similar amplification of AC stimulation was not seen with broken‐cell preparations.Most (60–70%) pineal guanylate cyclase (GC) was recovered in supernatant fractions after centrifugation of homogenates at 110,000 × g; this soluble GC was unaffected by potential agonists. Low concentrations (0.01–1 nM) of NE, ISO, and phenylephrine (PE) stimulated GC in impure and purified membrane fractions, but each inhibited at concentrations above 10 μM. All concentrations of ISO and NE inhibited GC in the presence of the a‐agonist PE. Melatonin alone did not affect particulate GC, but L‐ISO stimulation was not seen in the presence of equivalent concentrations of melatonin.The in vitro data are consistent with both α‐ and β‐receptor regulation of cyclic nucleotide metabolism in pinealocytes. Endogenous NE may differentially regulate cyclic AMP and guanosine‐3′, 5′‐cyclic monophosphate (cyclic GMP) in pineal; low NE concentrations that stimulate GC have only a slight effect on AC, but higher NE concentrations that inhibit GC maximally stimulate AC. Particulate GC and AC also were resolved by equilibrium centrifugation, to give several discrete peaks of enzyme activity. The results support the existence of several forms of AC and GC, which have different responses to adrenergic agonists.