Differential secretion of pro-opiomelanocortin peptides by the pars distalis and pars intermedia of beagle dogs.
Beagle dogs were given saline, insulin or the dopamine antagonist, haloperidol, to examine peripheral concentrations of immunoreactive (ir)-pro-opiomelanocortin (POMC) peptides resulting from pars distalis or pars intermedia stimulation. Six beagles were given each test substance on separate occasions with and without dexamethasone pretreatment. Plasma was assayed directly for glucose, ir-ACTH, ir-alpha-MSH, cortisol and, after Sephadex G-50 Fine gel filtration chromatography, for ir-beta-lipotrophin (ir-beta-LPH) and ir-beta-endorphin (ir-beta-END) content. Injection of 0.5 units insulin/kg lowered (P less than 0.01) plasma glucose from 4.9 +/- 0.3 mmol/l (mean +/- S.D., saline controls) to 2.3 +/- 0.5 mmol/l, coincident with increasing ir-ACTH (9.5 +/- 3.1 to 106 +/- 54 pmol/l), cortisol (52 +/- 27 to 221 +/- 27 nmol/l), ir-beta-LPH (not detectable to 34 +/- 18 pmol/l) and ir-beta-END (not detectable to 52 +/- 22 pmol/l). Plasma ir-alpha-MSH concentrations were not affected by insulin. Pretreatment with dexamethasone abolished the ir-ACTH, cortisol, ir-beta-LPH and ir-beta-END increases in response to 0.75 units insulin/kg. Haloperidol (1 mg/kg) increased (P less than 0.01) plasma ir-ACTH (to 103 +/- 63 pmol/l), cortisol (to 243 +/- 11 nmol/l), ir-beta-LPH (to 16 +/- 6 pmol/l), ir-beta-END (to 136 +/- 73 pmol/l) and additionally raised ir-alpha-MSH (7 +/- 8 pmol/l in saline controls to 131 +/- 80 pmol/l after haloperidol).(ABSTRACT TRUNCATED AT 250 WORDS)
Kemppainen
R J
RJ
Department of Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Alabama 36849.
Sartin
J L
JL
D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D003907:Dexamethasone; D004285:Dogs / Q000502:physiology*; D005260:Female; D006220:Haloperidol; D007328:Insulin; D008297:Male; D010446:Peptide Fragments / Q000378:metabolism*; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D011333:Pro-Opiomelanocortin / Q000378:metabolism*; D000521:alpha-MSH / Q000097:blood; D001615:beta-Endorphin / Q000097:blood; D008083:beta-Lipotropin / Q000097:blood
D001786:Blood Glucose; D007328:Insulin; D010446:Peptide Fragments; C028182:proopiocortin fragments; D000521:alpha-MSH; D001615:beta-Endorphin; D011333:Pro-Opiomelanocortin; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D008083:beta-Lipotropin; D006220:Haloperidol