Occurrence of an insulin-like peptide in extracts of peripheral nerves of th cat and in extracts of human vagal nerves.

Biopsies from various peripheral nerves were collected from living cats. The biopsies were extracted with acid ethanol and the insulin-like immunoreactivity (ILI) content of the extracts determined with radioimmunoassay. The vagal, sciatic and radial nerves contained on the average 90, 3 and 28 ng of ILI per gram nerve tissue (wet weight), respectively. In the sympathetic trunc no ILI was found. In order to partly purify and characterize the nerve ILI extracts these were run on an HPLC system. the ILI coeluted with standard bovine insulin. The same amounts of ILI were found in the nerve extracts whether run on the HPLC system or not. It can be concluded that all of the immunoreactive material of the nerve extracts corresponds to insulin or to a peptide very similar to insulin. In two cats the radial and sciatic nerves were ligated for 24 h. Two to ten times more ILI occurred in biopsies taken proximal to the site of ligation than in those from corresponding distal biopsies, indicating that the insulin-like material is transported distally within the nerves. ILI was found in extracts from vagal nerves taken from 3 days old human autopsy material. Also this human ILI coeluted with the bovine insulin standard in the HPLC system.