Concentration of porcine proinsulin-like material in plasma of insulin-treated diabetics in relation to purity of insulin preparations.

Porcine proinsulin-like Material (P-PLM) was determined in plasma from 25 juvenile diabetics previously treated for more than six years with crystalline porcine insulin and again after 2--2 1/2 years subsequent treatment with highly purified porcine insulin. As P-PLM in insulin preparations was reduced from 7 mmol/mol insulin to 0.1 mmol/mol insulin, so plasma concentrations of P-PLM were reduced from mean 166 pmol/l (range 34--428) to mean 27 pmol/l (range 13--64) on the same insulin dose. During the same period, the insulin-binding capacity of plasma showed a decrease.