The contaminating Proinsulin-Like Immunoreactivity (PLI) of several insulin preparations recently on the market was determined directly and after gel filtration by porcine and bovine proinsulin-specific radioimmunoassay.
Although gel filtration of 800 μg of Novo lente gelchromatographed insulin revealed neither porcine nor bovine Proinsulin-Like Components (PLC), apparent porcine and bovinePLC were detected after gel filtration of 800 μg of single peak insulin (lente insulin “Lilly” U-40, lente insulir “Lilly” U-100, regular insulin Iletin U-100) and 100 μg of Novo regular insulin by the specificradioimmunoassay.
The gelchromatographed insulin preparation contained less than 0.00045% of porcine and bovint PLI, but the regular insulin preparation from the same company contained 0.93 % of porcine and bovine PLI by weight as estimated directly with the specific-radioimmunoassay methods foi porcine and bovine PLI.
Single peak insulin preparations contained about 0.2 to 0.6% of porcine or bovine PLI by weight as estimated directly.
