Diuretic action and immunological cross-reactivity of corticotropin and locust diuretic hormone

A functional similarity and immunological cross-reactivity between adrenocorticotrophic hormone (ACTH) and a locust diuretic hormone (DH) is reported. The functional similarity is expressed in that ACTH mimics DH by stimulating fluid secretion and cyclic AMP (cAMP) secretion in locust Malpighian tubules. Desacetyl-alpha-melanocyte-stimulating hormone is active to a lesser degree but no other POMC-derived peptide tested was found to follow suit. Immunological cross-reactivity is shown by a positive response of HPLC-purified DH with a specific ACTH radioimmunoassay as well as a significant reduction in DH activity (fluid secretion) after incubations with ACTH antiserum. However, ACTH and DH are different peptides since they do not share common separation characteristics on HPLC and ACTH does not induce a high excess secretion of cAMP by the tubule cell as does DH.