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INTRINSIC PULSATILITY OF ACTH RELEASE FROM THE HUMAN PITUITARY IN VITRO
Author(s) -
GAMBACCIANI M.,
LIU J. H.,
SWARTZ W. H.,
TUEROS V. S.,
RASMUSSEN D. D.,
YEN S. S. C.
Publication year - 1987
Publication title -
clinical endocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 147
eISSN - 1365-2265
pISSN - 0300-0664
DOI - 10.1111/j.1365-2265.1987.tb00810.x
Subject(s) - endocrinology , medicine , pulsatile flow , egta , stimulation , pulse (music) , hypothalamus , acth secretion , in vitro , pituitary gland , chemistry , calcium , adrenocorticotropic hormone , hormone , biochemistry , engineering , detector , electrical engineering
SUMMARY An in‐vitro perifusion system was used to investigate spontaneous ACTH release from human fetal (21–23 weeks gestation) and adult pituitaries. The pattern of ACTH release from fetal pituitaries ( n = 7) exhibited a remarkable pulsatile character with a mean (± SEM) pulse interval of 11.3 ± 0.8 min. The mean pulse amplitude was 49.7 ± 6.3 pg, with a nadir to peak increment of 90.7 ± 10.4%. The mean ACTH release rate was 87.2±13.3 pg/2 min. Addition of the calcium chelator EGTA (4 nM) to the perifusion medium induced a significant ( p ±0.01) decrease in both ACTH release rate (from 102.0 ± 8.5 to 52.0 ± 9.9 pg/2 min) and ACTH pulse amplitude (from 57.7 ± 2.8 to 31.3 ± 4.6 pg) ( n = 3). Administration of either 2 nM corticotrophin releasing factor (CRF) or 56 mM KCl induced 10‐ and 2‐fold increases in ACTH secretion, respectively ( n = 2). Quarters of adult human pituitaries ( n – 6) also secreted ACTH in a pulsatile fashion, with a pulse interval of 14.8±1.7 min, pulse amplitude of 86.7± 10.0 pg, nadir to peak increment of 84.5 ± 9.8%, and overall release rate of 167.2 ± 8.8 pg/2 min. These studies demonstrate that ACTH release from the isolated human pituitary in vitro is characterized by high frequency/low amplitude pulses, independent of hypothalamic stimulation. Accordingly, this spontaneous calcium‐dependent pulsatile ACTH release apparently reflects the activity of an intrinsic intrapituitary pulse‐generating mechanism.