Schally A V, Redding T W, Arimura A, Dupont A, Linthicum G L
Veterans Administration Hospital, New Orleans, Louisiana.
Endocrinology. 1977 Mar;100(3):681-91. doi: 10.1210/endo-100-3-681.
A non-retarded fraction with prolactin-release inhibiting factor (PIF) activity obtained by chromatography of a concentrate of porcine hypothalami on carboxymethyl-cellulose was chromatographically distinct from catecholamines. This fraction was purified further by six steps involving chromatography on Sephadex G-25, countercurrent distribution, free-flow electrophoresis, and chromatography on triethylaminoethyl cellulose. The PIF-active substance was isolated and identified as gamma-amino-butyric acid (GABA) by: 1) amino acid analyses using sodium as well as lithium-based buffers for resolution of biological fluids, 2) thin-layer chromatography of underivatized material as well as phenylthiocarbamyl derivatives, and 3) mass spectroscopy. Natural and synthetic GABA inhibited prolactin, but not LH release in vitro from isolated rat pituitary halves at doses as low as 0.1 microgram/ml. The inhibition was proportional to the dose; natural and synthetic GABA possessed identical PIF activity. Synthetic GABA also decreased prolactin release in monolayer cultures of rat pituitary cells and inhibited TRH-stimulated prolactin release. The inhibition of prolactin release in vitro by GABA could not be blocked by perphenazine, which inhibits PIF activity of catecholamines. GABA also suppressed prolactin release in vivo, although large doses were needed. Either rapid iv injection or infusion of GABA in doses of 1 to 100 mg in rats significantly decreased serum prolactin levels, which were previously elevated by pretreatment with monoiodotyrosine perphenazine, chlorpromazine, haloperidol, or sulpiride. beta-hydroxy GABA significantly depressed prolactin release, but beta-(p-chlorophenyl)-GABA (Lioresal, CIBA) and 4 other analogs of GABA were not effective in vivo and/or in vitro. The results indicate that GABA can inhibit prolactin release by a direct action on the pituitary gland, but whether this effect is physiologically meaningful still remains to be determined.
通过将猪下丘脑浓缩物在羧甲基纤维素上进行色谱分离得到的具有催乳素释放抑制因子（PIF）活性的非阻滞级分，在色谱上与儿茶酚胺不同。该级分通过六个步骤进一步纯化，包括在葡聚糖凝胶G - 25上的色谱分离、逆流分配、自由流动电泳以及在三乙氨基乙基纤维素上的色谱分离。通过以下方法分离并鉴定出具有PIF活性的物质为γ-氨基丁酸（GABA）：1）使用基于钠和锂的缓冲液进行氨基酸分析以解析生物流体；2）对未衍生化物质以及苯硫代氨基甲酰衍生物进行薄层色谱分析；3）质谱分析。天然和合成的GABA在体外能抑制催乳素释放，但对分离的大鼠垂体半片在低至0.1微克/毫升的剂量下不抑制促黄体生成素（LH）释放。这种抑制作用与剂量成正比；天然和合成的GABA具有相同的PIF活性。合成的GABA还能降低大鼠垂体细胞单层培养物中的催乳素释放，并抑制促甲状腺激素释放激素（TRH）刺激的催乳素释放。奋乃静不能阻断GABA在体外对催乳素释放的抑制作用，而奋乃静可抑制儿茶酚胺的PIF活性。GABA在体内也能抑制催乳素释放，尽管需要大剂量。在大鼠中，快速静脉注射或输注1至100毫克的GABA可显著降低血清催乳素水平，这些血清催乳素水平此前因用单碘酪氨酸、奋乃静、氯丙嗪、氟哌啶醇或舒必利预处理而升高。β-羟基GABA能显著抑制催乳素释放，但β-（对氯苯基）-GABA（力奥来素，CIBA）和其他4种GABA类似物在体内和/或体外均无效。结果表明，GABA可通过直接作用于垂体来抑制催乳素释放，但这种作用在生理上是否有意义仍有待确定。
