Potency of biosynthetic human insulin determined in vitro

Biosynthetic human insulin (BHI) obtained from separately synthesized A- and B-chains by recombinant DNA technology with Escherichia coli fermentation was compared with human and pork insulin of high purity in vitro. Applying four biologic tests (glucose oxidation and glucose incorporation into the lipids by rat epididymal fat pads, inhibition of lipolysis, and ATP depletion of isolated fat cells) and three receptor assays (binding competition with human fat cells, IM-9 lymphocytes, and rat liver cell plasma membranes), we could not discern significant differences of the half-maximum response by these seven methods. The only variance occurred with the ATP-depletion assay. This method disclosed 10% greater maximum reversion of isoproterenol-induced ATP depletion by BHI when compared with pork insulin.