Homogeneous [mono-125I-Tyr10]- and [mono-125I-Tyr13] glucagon.
The two monoiodinated forms of glucagon were prepared by lactoperoxidase-catalysed iodination followed by separation by reversed-phase high-performance liquid chromatography. The intramolecular distribution of 125I was analysed by tryptic and chymotryptic cleavage of the isolated isomers. The results show that [mono-125I-Tyr10]- and [mono-125I-Tyr13]glucagon can be separated from each other and from the respective unlabelled polypeptide and thus can be obtained in a pure state with the highest possible specific activity. We have studied the receptor binding ability of both tracer isomers to isolated intact rat hepatocytes. The resulting Kd values were 2.0 +/- 0.2 nM for the tyrosine-13-labelled glucagon and 4.2 +/- 0.3 nM for the tyrosine-10-labelled glucagon.
D000818:Animals; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D002918:Chymotrypsin; D005934:Glucagon / Q000031:analogs & derivatives*; D006868:Hydrolysis; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D008099:Liver / Q000378:metabolism; D011869:Radioligand Assay; D051381:Rats; D014357:Trypsin; D014443:Tyrosine / Q000032:analysis*
D007457:Iodine Radioisotopes; D014443:Tyrosine; D005934:Glucagon; D002918:Chymotrypsin; D014357:Trypsin