Evidence that the insulin secretagogue, β-cell-tropin, is ACTH_22–39

Abstract

The pituitary neurointermediate lobe of genetically obese (ob/ob) mice contains a hormone which stimulates insulin release^1–3 and which cross-reacts with a -COOH-terminal ACTH antiserum, suggesting that it is related to corticotropin-like intermediate lobe peptide (CLIP), the 18–39 fragment of ACTH^4–6. The hormone, which we have called β-cell-tropin⁷, has been shown to be present in the plasma of the ob/ob mouse⁸ and to potentiate glucose induced insulin secretion⁹. We have now shown that ACTH_22–39 prepared by tryptic digestion of human synthetic CLIP behaves similarly on Biogel chromatography and on reverse-phase HPLC to the naturally occurring β-cell-tropin. Furthermore, β-cell-tropin and ACTH_22–39 have indistinguishable antigenic and insulin releasing properties.