Radioimmunoassay for non-suppressible insulin-like activity.
By immunizing rabbits--tolerant against the bulk of normal human serum proteins--with highly purified non-suppressible insulin-like activity (NSILA-S), an antiserum was obtained which made possible the development of a double-antibody radioimmunoassay. Its sensitivity is about 30 pg NSILA-S per tube or 150 pg NSILA-S/ml. The specificity exceeds that of the bioassay used for comparison which is based in the stimulation by NSILA-S of 125IUDR incorporation into chicken fibroblasts in culture. The radioimmunoassay is sufficiently sensitive and specific to allow direct NSILA-S measurement in serum or plasma samples of humans and experimental animals. In human plasma samples NSILA-S levels, carrying between less than 0.15 and 25 ng/ml , were found to have an average of about 4 ng/ml. In rats higher levels were observed with a mean of 7.7 ng/ml in 4-week-old animals, increasing to about 60 ng/ml in 6-month-old rats. In fasting rats the NSILA-S plasma level is reduced. In acid-treated samples of plasma considerably higher NSILA-S amounts are found.
D000818:Animals; D001681:Biological Assay; D001798:Blood Proteins / Q000378:metabolism; D002645:Chickens; D004285:Dogs; D005069:Evaluation Studies as Topic; D005347:Fibroblasts / Q000378:metabolism; D006041:Goats; D006801:Humans; D007065:Idoxuridine / Q000378:metabolism; D011817:Rabbits / Q000276:immunology; D011863:Radioimmunoassay / Q000379:methods; D051381:Rats; D013002:Somatomedins / Q000032:analysis*
D001798:Blood Proteins; D007065:Idoxuridine; D013002:Somatomedins