Leigh A J, Chapman A J, Shakil T, Wilson C A
Department of Obstetrics and Gynaecology, St George's Hospital Medical School, London, UK.
J Reprod Fertil. 1994 Jul;101(2):489-99. doi: 10.1530/jrf.0.1010489.
A comparison was made between the properties of LH derived from female rat pituitary glands and plasma. Samples were collected from adult intact rats 5 h before or at the time of the pro-oestrous preovulatory LH surge; 27-day-old rats untreated or given 5 IU pregnant mares' serum gonadotrophin (PMSG) s.c. on day 25, which induced LH release 54 h later and adult ovariectomized rats untreated or primed with either 5 micrograms oestradiol benzoate s.c. or 5 micrograms oestradiol benzoate followed 48 h later by 0.5 mg progesterone s.c., which induced LH release 4-6 h later. All pituitary LH samples were totally bound to an anionic ion-exchange resin (DE52), while only a small proportion of the plasma LH was bound. Only 0-10% plasma LH obtained from intact, ovariectomized (with and without steroids) and untreated immature rats was bound, while a greater proportion of bound LH (36%) was noted in rats treated with PMSG. Gel filtration indicated only slight differences between pituitary and plasma LH, the former eluting marginally earlier than whole plasma and the unbound and bound plasma forms derived after separation by DE52 resin. Affinity chromatography (Concanavalin A and Glycine maximus) showed that LH from both sources possesses high mannose oligosaccharides and that plasma LH does not bear terminal N-acetyl galactosamine residues, although 20% of the pituitary form does. Plasma obtained from pro-oestrous rats had greater bioactivity than had pituitary LH in stimulating testosterone from Leydig cells and progesterone from granulosa cells in vitro, and inducing ovulation in immature rats in vivo. Leydig cell bioassays for LH in fractions obtained from ion-exchange separation indicate that steroidogenic activity of unbound plasma LH is greater than bound pituitary LH when they were collected at times of enhanced release. When release was inhibited (oestrogen-primed ovariectomized rats or immature rats), the steroidogenic activity of plasma and pituitary LH were similar and an acidic steroidogenic component was present in the plasma that was not recognized immunogenically as LH. In summary, pituitary LH undergoes a conversion on release into the plasma that involves a change in binding characteristics on an ion-exchange resin. In conditions when LH release is enhanced there is an increase in bioactivity of plasma LH owing to modification either by steroids or some other plasma factor(s) that perhaps influence the structure of LH directly or by steroids acting indirectly to alter GnRH release, which then modifies LH structure. These structural changes are minor and probably involve alterations in the glycosyl attachments.
对源自雌性大鼠垂体和血浆的促黄体生成素（LH）的特性进行了比较。样本采自成年未处理大鼠，时间为动情前期排卵前LH峰前5小时或LH峰出现时；27日龄未处理大鼠，或于第25天皮下注射5国际单位孕马血清促性腺激素（PMSG）的大鼠，PMSG注射54小时后诱导LH释放；成年去卵巢大鼠，未处理或皮下注射5微克苯甲酸雌二醇，或皮下注射5微克苯甲酸雌二醇后48小时再皮下注射0.5毫克孕酮，分别在注射后4 - 6小时诱导LH释放。所有垂体LH样本都完全结合到一种阴离子交换树脂（DE52）上，而血浆中只有一小部分LH能结合。从未处理的成年、去卵巢（有无激素处理）和未成熟大鼠获得的血浆LH中，只有0 - 10%能结合，而在PMSG处理的大鼠中，结合的LH比例更高（36%）。凝胶过滤显示垂体LH和血浆LH之间只有细微差异，前者的洗脱时间略早于全血浆以及DE52树脂分离后得到的未结合和结合血浆形式。亲和层析（伴刀豆球蛋白A和大豆凝集素）表明，两种来源的LH都具有高甘露糖寡糖，血浆LH不带有末端N - 乙酰半乳糖胺残基，而20%的垂体LH带有。动情前期大鼠的血浆在体外刺激睾丸间质细胞产生睾酮和颗粒细胞产生孕酮，以及在体内诱导未成熟大鼠排卵方面，比垂体LH具有更高的生物活性。对离子交换分离得到的组分进行LH的睾丸间质细胞生物测定表明，在LH释放增强时收集的未结合血浆LH的类固醇生成活性大于结合的垂体LH。当释放受到抑制时（雌激素预处理的去卵巢大鼠或未成熟大鼠），血浆和垂体LH的类固醇生成活性相似，血浆中存在一种酸性类固醇生成成分，其在免疫原性上不被识别为LH。总之，垂体LH释放到血浆中时会发生转化，这涉及到在离子交换树脂上结合特性的改变。在LH释放增强的情况下，血浆LH的生物活性增加，这是由于类固醇或其他一些血浆因子的修饰作用，这些因子可能直接影响LH的结构，或者通过类固醇间接作用改变促性腺激素释放激素（GnRH）的释放，进而修饰LH的结构。这些结构变化较小，可能涉及糖基连接的改变。
