Regulation of pro-adrenocorticotropin-endorphin synthesis and secretion in cultured neonatal rat anterior pituitary.
Previous work demonstrated that newborn rat anterior pituitary corticotropes display processing patterns for pro-ACTH/endorphin that are different from the adult. The synthesis and release of beta-endorphin-related peptides was examined in dispersed cell and explant cultures of newborn anterior pituitary to investigate corticotrope development further. The temporal pattern of pro-ACTH/endorphin processing differed significantly from adult rat melanotropes and AtT-20 cells. While pro-ACTH/endorphin processing begins within 30 min of synthesis in adult melanotropes and AtT-20 cells, pulse-labeling of newborn corticotropes in culture indicated that pro-ACTH/endorphin remained uncleaved for at least 90 min after synthesis. With further incubation, there was a decrease in radioactivity associated with the precursor and an equivalent rise in the radioactivity associated with beta-endorphin and beta-lipotropin. However, unprocessed precursor still remained in the cultured newborn anterior pituitary cells after a 25-h chase. Although intact pro-ACTH/endorphin from newborn corticotropes was very long-lived, the precursor did undergo oligosaccharide maturation and became endoglycosidase H resistant within 1 h after synthesis. Similar to the adult, pro-ACTH/endorphin synthesis was doubled in cultures of newborn anterior pituitary chronically treated with 10 nM CRF resulting in a 3- to 4-fold stimulation of secretion over the basal rate. However, unlike the AtT-20 cell or adult rat corticotrope, the proteolytic processing of pro-ACTH/endorphin in the newborn corticotrope was altered by chronic secretagogue treatment; less pro-ACTH/endorphin was converted to beta-endorphin in secretagogue-treated corticotropes than in controls. Thus processing of pro-ACTH/endorphin in the corticotrope is not mature by birth and can be regulated by chronic CRF treatment.
Sato
S M
SM
Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
Mains
R E
RE
D000118:Acetylglucosaminidase; D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D002478:Cells, Cultured; D004723:Endorphins / Q000378:metabolism*; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D015335:Molecular Probes; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism*; D011233:Precipitin Tests; D011498:Protein Precursors / Q000096:biosynthesis* / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000502:physiology; D051381:Rats; D013462:Sulfur Radioisotopes
D004723:Endorphins; D015335:Molecular Probes; D011498:Protein Precursors; D013462:Sulfur Radioisotopes; D000324:Adrenocorticotropic Hormone; D000118:Acetylglucosaminidase; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase