Altered ratios of beta-endorphin: beta-lipotropin released from anterior lobe corticotropes with increased secretory drive. I. Effects of diminished glucocorticoid secretion.
Previous studies have demonstrated that acute stress or ovine corticotropin-releasing hormone (oCRH) in vivo, or oCRH in vitro, stimulates release of beta-endorphin over beta-lipotropin from anterior pituitary corticotropes. This occurs despite the predominance of beta-lipotropin in corticotrope peptide stores. In vitro studies with primary anterior pituitary cultures suggested that chronic exposure to oCRH results in a shift towards more beta-lipotropin secretion into the media than with short-term exposure. The current studies explored whether increased secretory drive in vivo results in a similar shift towards more beta-lipotropin. We used removal of glucocorticoids by adrenalectomy or metyrapone blockade of corticosterone synthesis, to stimulate endogenous secretion of CRH and vasopressin. Both treatments resulted in shifts of the ratio of beta-endorphin: beta-lipotropin in plasma of experimental animals in comparison to the sham-treated control rats. In vitro testing with oCRH of anterior lobe cultures from adrenalectomized or metyrapone-treated rats demonstrated similar effects of these treatments on the ratio of beta-endorphin:beta-lipotropin. These changes occurred despite similar ratios of beta-endorphin:beta-lipotropin in anterior pituitary peptide stores.
Young
E A
EA
Department of Psychiatry, University of Michigan, Ann Arbor 48109.
Przewlocki
R
R
Patel
P
P
Watson
S J
SJ
Akil
H
H
D000315:Adrenalectomy; D000818:Animals; D002850:Chromatography, Gel; D005246:Feedback / Q000502:physiology; D005938:Glucocorticoids / Q000502:physiology*; D066298:In Vitro Techniques; D008297:Male; D008797:Metyrapone / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley; D012756:Sheep; D001615:beta-Endorphin / Q000096:biosynthesis / Q000276:immunology / Q000378:metabolism*; D008083:beta-Lipotropin / Q000096:biosynthesis / Q000276:immunology / Q000378:metabolism*
D005938:Glucocorticoids; D001615:beta-Endorphin; D008083:beta-Lipotropin; D008797:Metyrapone