β-Core fragments are contaminants of the World Health Organization Reference Preparations of human choriogonadotrophin and its α-subunit

Publisher Website
Google Scholar
Abstract
Highly purified preparations of human choriogonadotrophin (hCG), hCGα and hCGβ, including those preparations which are being distributed by the World Health Organization as International Standards, cross-reacted in a new radioimmunoassay with increased relative specificity for the β-core fragment of hCG. A major portion of the β-core immunoreactivity in the hCG and hCGα preparations eluted from Sephadex G-100 in a position (approximate apparent molecular size 15 000–18 000) corresponding to that of purified β-core fragment prepared from pregnancy urine. However, in the case of hCGβ-subunit preparations, virtually all of the β-core cross-reacting material eluted from Sephadex G-100 in the same fractions as the native hCGβ-subunit. Quantitatively, the cross-reacting β-core material accounts for less than 1% (w/w) of the total hCG or subunit immunoreactivity, as measured by conventional radioimmunoassays. The presence of the β-core fragments as discrete molecular components of the hCG and hCGα preparations should be borne in mind when these preparations are used to calibrate new radioimmunoassays for hCG-related molecules. J. Endocr. (1988) 117, 147–152