A radioimmunoassay for circulating @entity1 XXXX .

@entity1 @entity6 @entity840 @entity4151 @entity2690 @entity413
A radioimmunoassay for @entity1 @entity2690 ( @entity4151 ) has been developed using biosynthetic @entity4151 prepared by recombinant DNA technology as immunogen, standard, and tracer. The antiserum was raised in a @entity840 and then adsorbed against insulin and C-peptide conjugated to Sepharose to improve its specificity. After adsorption of the antiserum, the cross-reactivities to insulin and C-peptide were each less than 0.2%. Competition studies using in vitro enzymatically split forms of @entity2690 demonstrated that the major antigenic determinant recognized was the junctional region between the B-chain of insulin and the C-peptide. The range of the assay extended from 10 to 150 fmol/tube, with a 50% displacement of 45-55 fmol/tube. This sensitivity proved suitable for measurements of serum @entity4151 concentrations during infusion of biosynthetic @entity4151 into normal subjects and type I @entity6 subjects. Eighty-five of 89 serum samples from the normal subjects and each of 20 samples from @entity6 subjects diluted in parallel with the @entity4151 standard. Since the direct assay sensitivity was not sufficient for measurement of endogenous @entity4151 levels, a simple procedure for quantitative extraction of @entity2690 -like material (PLM) from up to 40 ml of plasma on insulin antibody-Sepharose columns was developed. Logit-log slopes were calculated for dilutions of extracts of samples collected in the fasting state and 60 min after 75 g or oral @entity413 from eight healthy subjects. The slopes of 15 of the 16 samples did not differ significantly from the slope of the @entity4151 standard.(ABSTRACT TRUNCATED AT 250 WORDS)
