The effect of fetal hypophysectomy with or without ACTH replacement on the molecular weight profile of enkephalin-containing peptides in the adrenal medulla of the fetal sheep.
We have investigated the possible role of the fetal pituitary and ACTH in the control of the synthesis and post-translational processing of the enkephalin precursor, proenkephalin A (proEnk A), in the fetal sheep adrenal gland in late gestation. Fetal hypophysectomy (n = 8) or sham operations (n = 4) were performed between 109 and 118 days of gestation. At 138-139 days, either ACTH(1-24) (10.5 micrograms/0.24 ml saline per h, n = 4) was infused intravenously for 72 h into hypophysectomized fetal sheep or 0.9% (w/v) NaCl alone (0.24 ml/h, n = 4) was infused for 72 h into hypophysectomized fetal sheep and sham-operated animals. At the end of the infusion the pregnant ewe was killed and left or right adrenal glands (n = 12) were collected from the fetal sheep that were intact and given saline (Intact + sal; n = 4), hypophysectomized and given saline (Hx + sal; n = 4) and hypophysectomized and given ACTH (Hx + ACTH; n = 4). Each adrenal was homogenized in acid (acetic acid (1 mol/l)/HCl (20 mmol/l)/2-mercaptoethanol (0.2%)). After centrifugation, the supernatant was loaded onto a Sephadex G-75 column (2.0 x 50 cm), eluted at 80 ml/24 h and fractions were collected (5 ml, n = 42). An aliquot of each fraction (2 ml) was dried down prior to enzymatic digestion (trypsin/carboxypeptidase B) and oxidation with H2O2, and assay for methionine-O-enkephalin (immunoreactive Met-O-Enk).(ABSTRACT TRUNCATED AT 250 WORDS)
Coulter
C L
CL
Department of Physiology, Monash University, Clayton, Victoria, Australia.
Young
I R
IR
Browne
C A
CA
McMillen
I C
IC
D000313:Adrenal Medulla / Q000187:drug effects / Q000196:embryology* / Q000378:metabolism; D000324:Adrenocorticotropic Hormone / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D004744:Enkephalin, Methionine / Q000378:metabolism; D004745:Enkephalins / Q000378:metabolism*; D005333:Fetus / Q000601:surgery; D007016:Hypophysectomy; D008970:Molecular Weight; D011498:Protein Precursors / Q000378:metabolism*; D011863:Radioimmunoassay; D012756:Sheep / Q000196:embryology* / Q000378:metabolism
D004745:Enkephalins; D011498:Protein Precursors; C029992:proenkephalin; D004744:Enkephalin, Methionine; D000324:Adrenocorticotropic Hormone