Peptide hormones in strange places--are they there?

Are ACTH and insulin synthesized in tissues other than the pituitary and pancreas, respectively? ACTH and TSH are widely distributed in the rat brain but are restricted to the hypothalamic regions of the primate brain. It is concluded that these pituitary peptides are not synthesized in the brain in extrahypothalamic sites. The apparent immunoreactive ACTH in pancreas and gastrointestinal tract does not have the physicochemical characteristics of any known form of ACTH and thus is probably an artifact of some radioimmunoassay systems. Concentrations of insulin in acid-ethanol extracts of brains of rats and some other animals are generally less than plasma concentrations while concentrations in kidney extracts are about ten-fold plasma levels. The use of octadecylsilyl silica cartridges permits up to a hundred-fold concentration of insulin in acid-ethanol tissue extracts with recoveries greater than 75--85 percent. With this methodology it is observed that pork-like insulin in guinea pig tissues is less than 20 pg/g in contrast to the ng/g levels reported by others. It is concluded that ACTH and insulin are not brain/gut peptides and that guinea pig tissues do not contain measurable pork-like insulin in several radioimmunoassay systems.