[Immuno-reactive insulin-like substances in the rat].

Chromatography on G50 or G100 sephadex column of rat plasma or serum divides up the insulin-like immunoreactive material into three peaks: monomere insulin, proinsulin and a fraction of molecular weight between 50 and 100,000. This fraction is virtually absent (less than 1%) from immunoreactive material extracted from the pancreas. Comparison of the results obtained by methods using double or simple antibodies (charcoal dextran) and study of fixation in vitro of labelled insulin, taken up by various plasma proteins, suggest that the high molecular weight material includes insulin more or less broken down and linked to proteins. Furthermore, when one uses a double antibody method, the alpha globulins and albumin in the rat present also an insulin-like reactivity. This disadvantage does not occur with the charcoal dextran method which is more specific.