Failure to Demonstrate “Bound” Insulin in Human Serum

Abstract

The reported insulin-like activity, ILA, eluted from a cation resin column, following passage of serum, has been confirmed using the rat diaphragm bioassay. Four methods reported to convert “bound” to “free ” insulin did not increase assayable ILA. A quantitative estimate of ILA in the untreated preparation using the rat diaphragm assay was greater than the estimate obtained using the mouse in vivo assay. It is concluded that rat diaphragm measures total ILA without prior activation. These studies fail to support the concept of “free” and “bound” insulin in human serum.

Characteristics of Nonsuppressible Insulin-like Activity in Fasting Human Serum

“…As previously reported 19 we find that the eluate from the cation resin column, which Antoniades has labeled "bound insulin," possesses activity in the rat diaphragm bioassay without prior activation by any of the methods proposed by Antoniades et al 14 -25 and Gundersen and Lin. 26 We found no increase in ILA after any of the proposed methods of activation.…”

“…As previously reported, 19 we have not been able to confirm the activation of "bound" insulin by any of the methods proposed by Antoniades. We have greatly increased the activity of the original serum both by column fractionation and extraction.…”