2つの異なるRIA系を用いた胎児組織中のImmunoreactive GIF

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Since the discovery of the structures of somatostatin (GIF) in 1973 by Brazeau et al, its measurement by the radioimmunoassay (RIA) methods has been reported by Arimura et al (1975), Yanaihara et al (1978) and Sawano et al (1978). As GIF does not contain tyrosine and histidine, which can be radioiodized, analogues of GIF are being used as tracers in its radioimmunoassay. In this study, two different types of trafcers (125 I tyr8of GIF and 125I-tyrosyl-GIF) were used in RIA to measure the immunoreactive GIF of fetal tissues, and their results were compared. A highly specific anti-GIF serum was generated by immunizing rabbits with GIFconjugated BSA. 125 I-tyr8-GIF and 125I-tyrosyl-GIF were prepared by the lactoperoxidase method. The former was purified through a carboxymethylcellulose column and the latter through a Sephadex G-25 (fine) column. They were then incubated at 4°C in 0.01 M phosphate buffer saline containing 0.1% geratin and 0.2% BSA and used as tracers to measure the immunoreactive GIF-like substances in the pituitary gland, hypothalamus, pancreas, cerebrum, cerebellum, thyroid gland, stomach, small intestine and spinal cord of three fetuses obtained through legal abortion with gestation ages of 22 weeks, 23 weeks and 25 weeks. The free and bound forms were separated with the double antibody technique. The correlation of these GIF concentrations by the two different assay systems with results such as Y=0.905X- 87.4, r=0.992 and P<0.001 was demonstrated. From the displacement curves of the GIF-analogues (tyrosyl-GIF and tyr1 -GIF) and the standard curves of the synthetic GIF, it was found that when 125I-tyr8-GIF was used as the tracer, the anti-GIF serum could identify both the GIF-analogues and the synthetic GIF as the same substance; however, when 125I-tyrosyl-GIF was substituted as the tracer, the anti-GIF serum could only identify the tyrosyl-GIF and the synthetic GIF as being the same substance and excluded the tyr1 -GIF when its concentration reached beyond a certain level. The dilution curves of the immunoreactive-GIF extracted from the hypothalamus and pancreas of the fetuses were found to be parallel to the standard curves obtained by the synthetic GIF in both asssay systems. It is concluded that the two different assay systems which were used to measure the GIF concentrations in the fetuses can yield the same results and are useful in the application of GIF-RIA, but 125 I-tyr 8 -GIF is more stable than the 125I-tyrosyl-GIF.
日本内分泌学会の論文

2つの異なるRIA系を用いた胎児組織中のImmunoreactive GIF

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