Pars Intermedia ACTH and MSH Content: Effect of Adrenalectomy, Gonadectomy and a Neurotropic (Noise) Stress

Abstract

Pars intermedia (PI) ACTH and melanocyte-stimulating hormone (MSH) content and pars distalis (PD) ACTH concentration were measured following 3 experimentally induced ‘perturbations’. The feedback-induced increase in ACTH release following adrenalectomy is not accompanied by a change in PI ACTH and MSH contents, while the feedback-induced increase in gonadotropin secretion following gonadectomy is associated with significant changes in PI ACTH and MSH contents. A well-defined neurotropic (noise) stressor resulted in significant increases in PI ACTH and MSH. A striking finding in all of the studies was a positive correlation between PI ACTH and MSH contents. We conclude that PI ACTH and MSH secretion are altered with feedback-induced alterations in gonadotropin secretion and with neurotropic stressors.

Experimental Alterations of Endorphin Levels in Rat Pituitary

“…Small elevations in both neurointermediate lobe ACTH and MSH, together with reduc tions in content of anterior lobe ACTH have been reported to occur in the rat following audiogenic stress [Kraicer et al, 1977], It is tempting to correlate the marked similarity in secretory patterns of ACTH, MSH and ENDs, and to suggest that stress-induced de pletions in gland END content may reflect opioid peptide release from anterior lobe, with increased synthesis of hormonal stores in neurointermediate lobe.…”

ACTH and Corticosterone Secretion in Rats following Removal of the Neurointermediate Lobe of the Pituitary Gland

“…Miahle-Voloss [23] and Rochefort et al [33] proposed that the posterior pituitary gland was the princi pal source of ACTH during neurotropic vs. systemic stress, based on 'depletion' of material with ACTH bioactivity from the neurointermediate lobe (NIL) vs. anterior pitui tary lobe. Kraicer et al [22] disputed this interpretation when using a dispersed adrenal cell bioassay for pituitary ACTH contents. Conclusions about the importance of NIL ACTH in stress-induced hormone release were not forth coming from such experiments since (1) tissue content re flects balance among all the intracellular secretory pro cesses without necessarily providing and accurate indica tion of acute hormone release [22], and (2) ACTH bioassay may include activity of non-ACTH peptides that potentiate the effects of ACTH at the target tissue [28].…”

“…Kraicer et al [22] disputed this interpretation when using a dispersed adrenal cell bioassay for pituitary ACTH contents. Conclusions about the importance of NIL ACTH in stress-induced hormone release were not forth coming from such experiments since (1) tissue content re flects balance among all the intracellular secretory pro cesses without necessarily providing and accurate indica tion of acute hormone release [22], and (2) ACTH bioassay may include activity of non-ACTH peptides that potentiate the effects of ACTH at the target tissue [28].…”

Distribution of Crooke's cells and ACTH cells in the human pituitary glands.

“…In rats, ACTH and MSH content in the pars intermedia was not changed by adrenalectomy, but increased by gonadectomy and a neurotropic (noise) stress (Kraicer et al 1977). It requires further investigation to clarify whether or not the ACTH cells of intermediate lobe origin are unlikely to show Crooke's hyaline change.…”