Conventional insulin preparations (Novo), 5 times recrystallized, were contaminated with approximately 1 to 2 % proinsulin-like substances. Anti-insulin antibodies and even proinsulin-specific antibodies were found in many cases of diabetics treated with these insulin preparations. Monocomponent insulin, purified in order to eliminate its antigenicity for insulin, appeared to be less immunogenic than conventional insulin.
In this study, the contaminating proinsulin-like substances in Monocomponent Lente insulin (Batch 522*5), Monocomponent Actrapid insulin (Batch 500*5) and conventional Lente insulin (Lot. No.297961) were estimated directly and after gel filtration by porcine proinsulin-speufic specific radioimmunoassay.
Although gel filtration of conventional insulin (500 ng) revealed proinsulin-like components (PLC), these PLC were not detectable after gel filtration of 500 ng and 5000 ng of Monocomponent insulin by specific radioimmunoassay.
Monocomponent insulin preparations contained less than O.0001% of porcine proinsulin-like immunoreactivity (PLI) by weight as estimated directly utilizing specific radioimmunoassay for porcine PLI.
