Production and Evaluation of Anti-Gastrin Serum for Radioimmunoassay

방사면역측정을 위한 항 Gastrin 혈청의 생산 및 평가

In order to produce antibody for use in radioimmunoassay of gastrin in physiological concentration, four rabbits of New Zealand white were immunized with synthetic human gastrin-17-I conjugated to hemocyanin with EDC. Among them, only one rabbit produced antibody that could bind 50% of $^{125}I-gastrin$ at a final dilution of 1:25,000. $^{125}I-gastrin$ was prepared with synthetic human gastrin-17-I and $NaI^{125}$ by lactoperoxidase technique. The product was then purified on a column of Sephadex Gl5/G5O (7:3, w/w) followed by a column of DEAE sephadex A-25. The specific radioactivity of the purified $^{125}I-gastrin$ was in the range of 347-1429 ${\mu}Ci/nmole$ when determined by the self-displacement method. The effective affinity constant $(K_{eff})$, total binding sites (N), heterogeneity index $({\alpha})$ and average affinity constant $(K_{0})$ of the anti-gastrin serum calculated from Scatchard plot as well as Sips plot were $1.77{\times}10^{11}/M$, 255 nM, 0.84 and $0.79{\times}10^{11}/M$, respectively. When radioimmunoassay was performed with the anti-gastrin serum, it was confirmed that the mean concentration of gastrin immunoreactivity in plasma was increased by feeding in humans and rats, and also increased by bombesin administration in rats. The results indicate that the anti-gastrin serum produced in the present investigation is suitable for radioimmunological determination of gastrin in physiological concentration.

New Zealand white 계의 토끼에게 EDC를 사용하여 hemocyanin에 접합시킨 human G-17-I을 면역한 결과 gastrin의 방사면역측정에 적합한 항 gastrin 혈청을 얻는데 성공하였다. 본 실험에서 얻은 항 gastrin 혈청의 역가는 1:25,000이며 human G-17-I과 human big gastrin에 매우 친화력이 높은 반면 다른 위장관 peptide 들과는 교차반응성이 아주 낮았다. 본 항 gastrin 혈청의 effective affinity constant는 $1.77{\times}10^{11}/M$이었다. 또한 총 결합부위(total binding sites)는 255 nM, 이질성지수(heterogeneity index)는 0.84 그리고 average affinity constant는 $0.79{\times}10^{11}/M$이었다. 본 실험에서 얻은 항 gastrin 혈청을 사용하여 사람과 흰쥐의 혈장 gastrin 농도를 방사면역측정법으로 측정한 결과 이미 잘 알려진 결과와 동일한 성적을 얻을 수 있었다. 이러한 결과들을 종합하여 볼때 본 실험에서 얻은 항 gastrin 혈청은 생리적농도로 존재하는 gastrin의 방사면역측정에 적합한 것으로 생각된다.