Evidence for an ultradian secretion of adrenocorticotropin, β-endorphin and α-melanocyte-stimulating hormone by the ovine anterior and intermediate pituitary

Abstract

These studies were undertaken to characterize the secretion of the proopiomelanocortin (POMC)-peptides adreuocorticotropin (ACTH), immunoreactive (ir)-β-endorphin (β-EP), and ir-α-mclanoeyte-stimulating hormone (α-MSH) in the conscious sheep. When blood samples were taken at 10-min intervals, a distinct POMC-peptide and Cortisol ultradian rhythm was observed, and 4 of the 7 possible POMC-peptidc pulse patterns were defined. Three of these patterns included pulsatile ACTH secretion, and 70% were followed by a rise in plasma Cortisol. The fourth pulse pattern consisted of concordant ir-β-EPand ir-α-MSH secretion and was not temporally correlated with Cortisol secretion. When an intensified rat..