A dissociation between the adrenal and extra-adrenal actions of corticotrophin by periodate oxidation

Abstract

The adrenal and extra-adrenal activities of corticotrophin A1 and periodate[long dash]borohydride-treated corticotrophin A1 have been compared in vivo and in vitro. Periodate[long dash]borohydride treatment of corticotrophin leads to marked loss of adrenal-stimulating activity as assayed by the plasma-corticosterone response in hypophysectomized rats, but to a less complete loss of activity as judged from stimulation of steroidogenesis by adrenal slices in vitro. Periodate-borohydride-treated corticotrophin retains reduced but significant activity compared with corticotrophin A1 when tested for four extra-adrenal activities stimulation of fatty acid release from, and glucose uptake by, rat epididymal adipose tissue in vitro, adipokinetic effect in female mice and hypoglycaemia in starved male mice. The significance of the dissociation between adrenal and extra-adrenal actions of corticotrophin by modification of the N-terminal serine residue of corticotrophin is discussed in relation to the structure and function of the peptide.