Haro L S, Lee D W, Singh R N, Bee G, Markoff E, Lewis U J
Lutcher Brown Department of Biochemistry, Whittier Institute for Diabetes and Endocrinology, La Jolla, California 92037.
J Clin Endocrinol Metab. 1990 Aug;71(2):379-83. doi: 10.1210/jcem-71-2-379.
The receptor-binding properties of monomeric nonglycosylated human PRL (hPRL), glycosylated hPRL that does not bind to Concanavalin-A-Sepharose (G1-hPRL) and glycosylated hPRL that binds to Concanavalin-A-Sepharose (G2-hPRL) were tested in the lactating rabbit mammary gland RRA for lactogenic hormones. Variations in the glycosylation pattern of G-hPRL altered its receptor-binding properties, suggesting that the site of glycosylation may be proximal to the receptor-binding region. Relative potencies for the displacement of [125I]hPRL by hPRL, G1-hPRL, and G2-hPRL were 100%, 40%, and 26%, respectively. Relative potencies for displacement of [125I]G1-hPRL by hPRL, G1-hPRL, and G2-hPRL were 100%, 44%, and 69%, respectively; however, the displacement curve for G2-hPRL was not parallel to the others. When G2-hPRL was radiolabeled, there was no specific binding to lactogenic receptors. The presence of PRL receptor subtypes and/or kinetic cooperativity was suggested by the complexity of the binding isotherms. The immunoreactivities of the PRLs were tested in a homologous RIA, using polyclonal antiserum. The modification of the glycosylation pattern of hPRL significantly altered the RIA values for PRL. When hPRL was used as the radiotracer, the percent cross-reactivities of hPRL, G1-hPRL, and G2-hPRL were approximately 100%, 23%, and 17%, respectively. When G1-hPRL was used as the radiotracer, the percent cross-reactivities were approximately 100%, 135%, and 54% for hPRL, G1-hPRL, and G2-hPRL; however, the displacement curve for hPRL was not parallel to those of the glycosylated hPRLs. When G2-hPRL was used as the radiotracer, the percent cross-reactivities were approximately 100%, 32%, and 37% for hPRL, G1-hPRL, and G2-hPRL. These data point out that the glycosylation heterogeneity of hPRL is a factor that affects the diagnostic accuracy of hPRL determinations. Specific RIAs for each PRL are needed so that we can have valid and reliable measurements of each PRL isoform and consequently gain a better understanding of PRL's complex biological role.
在泌乳兔乳腺放射受体分析法（RRA）中，检测了用于检测催乳激素的单体非糖基化人催乳素（hPRL）、不与伴刀豆球蛋白A-琼脂糖结合的糖基化hPRL（G1-hPRL）以及与伴刀豆球蛋白A-琼脂糖结合的糖基化hPRL（G2-hPRL）的受体结合特性。G-hPRL糖基化模式的变化改变了其受体结合特性，这表明糖基化位点可能靠近受体结合区域。hPRL、G1-hPRL和G2-hPRL对[125I]hPRL的取代相对效价分别为100%、40%和26%。hPRL、G1-hPRL和G2-hPRL对[125I]G1-hPRL的取代相对效价分别为100%、44%和69%；然而，G2-hPRL的取代曲线与其他曲线不平行。当G2-hPRL被放射性标记时，与催乳激素受体没有特异性结合。结合等温线的复杂性提示存在催乳素受体亚型和/或动力学协同性。使用多克隆抗血清，在同源放射免疫分析（RIA）中检测了催乳素的免疫反应性。hPRL糖基化模式的改变显著改变了催乳素的RIA值。当hPRL用作放射性示踪剂时，hPRL、G1-hPRL和G2-hPRL的交叉反应百分率分别约为100%、23%和17%。当G1-hPRL用作放射性示踪剂时，hPRL、G1-hPRL和G2-hPRL的交叉反应百分率分别约为100%、135%和54%；然而，hPRL的取代曲线与糖基化hPRL的曲线不平行。当G2-hPRL用作放射性示踪剂时，hPRL、G1-hPRL和G2-hPRL的交叉反应百分率分别约为100%、32%和37%。这些数据指出，hPRL的糖基化异质性是影响hPRL测定诊断准确性的一个因素。需要针对每种催乳素的特异性RIA，以便我们能够对每种催乳素同工型进行有效且可靠的测量，从而更好地理解催乳素复杂的生物学作用。
