Electrical properties of cultured human adrenocorticotropin-secreting adenoma cells: Effects of high K+, cortocotropin-releasing factor, and angiotensin II

P. Mollard, P. Vacher, J. Guerin, Michael A Rogawski, B. Dufy

Research output: Contribution to journalArticle

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Abstract

ACTH-secreting pituitary adenoma cells were cultured from specimens obtained by transphenoidal hypophysectomy in five patients with Cushing's disease. The majority of adenoma cells (90%) stained specifically with antiserum against human ACTH. The electrophysiological properties and response to hormones of these cells were studied with intracellular recording techniques under current clamp conditions. Most (80%) of the cells fired action potentials that were Ca2+-dependent inasmuch as they were blocked by Co2+ (5 mM) and by removal of Ca2+ from the medium, but were unaffected by tetrodotoxin (0.3 mM) and by Na+ removal. The cells responded to factors known to stimulate ACTH release, including high K+, CRF, and angiotensin II (AII). High K+ (50 mM) induced a membrane depolarization in association with an increase in conductance. CRF (100 nM) produced a depolarization, a decrease in conductance, an increase in spike firing, and an increase in spike duration. Although AII was inactive in ordinary recordings, in cells loaded with lithium (Li+) to promote the phospholipid-dependent second messenger system, the peptide produced an increase in spike firing and spike duration with no change in membrane potential. The combination of CRF and AII (CRF + AII; 100 nM each) in Li+-loaded cells caused a greater excitatory effect than either peptide alone. Under voltage clamp, the response either to CRF or to CRF + AII could be attributed, at least in part, to the inhibition of a slow, voltage-dependent K+ current that is persistently active at resting potential. These results indicate that modulation of action potential firing may be an early step in the regulation of ACTH release from pituitary cells by known secretagogues. Since action potentials in these cells are associated with Ca2+ entry, the resulting changes in intracellular Ca2+ levels could mediate the effects of the hormones on secretion.

Original languageEnglish (US)
Pages (from-to)395-405
Number of pages11
JournalEndocrinology
Volume121
Issue number1
StatePublished - 1987
Externally publishedYes

Fingerprint

Angiotensin II
Adenoma
Adrenocorticotropic Hormone
Action Potentials
Membrane Potentials
ACTH-Secreting Pituitary Adenoma
Hormones
Pituitary ACTH Hypersecretion
Hypophysectomy
Peptides
Tetrodotoxin
Second Messenger Systems
Lithium
Immune Sera
Cultured Cells
Phospholipids
Membranes

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

Cite this

Electrical properties of cultured human adrenocorticotropin-secreting adenoma cells : Effects of high K+, cortocotropin-releasing factor, and angiotensin II. / Mollard, P.; Vacher, P.; Guerin, J.; Rogawski, Michael A; Dufy, B.

In: Endocrinology, Vol. 121, No. 1, 1987, p. 395-405.

Research output: Contribution to journalArticle

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abstract = "ACTH-secreting pituitary adenoma cells were cultured from specimens obtained by transphenoidal hypophysectomy in five patients with Cushing's disease. The majority of adenoma cells (90{\%}) stained specifically with antiserum against human ACTH. The electrophysiological properties and response to hormones of these cells were studied with intracellular recording techniques under current clamp conditions. Most (80{\%}) of the cells fired action potentials that were Ca2+-dependent inasmuch as they were blocked by Co2+ (5 mM) and by removal of Ca2+ from the medium, but were unaffected by tetrodotoxin (0.3 mM) and by Na+ removal. The cells responded to factors known to stimulate ACTH release, including high K+, CRF, and angiotensin II (AII). High K+ (50 mM) induced a membrane depolarization in association with an increase in conductance. CRF (100 nM) produced a depolarization, a decrease in conductance, an increase in spike firing, and an increase in spike duration. Although AII was inactive in ordinary recordings, in cells loaded with lithium (Li+) to promote the phospholipid-dependent second messenger system, the peptide produced an increase in spike firing and spike duration with no change in membrane potential. The combination of CRF and AII (CRF + AII; 100 nM each) in Li+-loaded cells caused a greater excitatory effect than either peptide alone. Under voltage clamp, the response either to CRF or to CRF + AII could be attributed, at least in part, to the inhibition of a slow, voltage-dependent K+ current that is persistently active at resting potential. These results indicate that modulation of action potential firing may be an early step in the regulation of ACTH release from pituitary cells by known secretagogues. Since action potentials in these cells are associated with Ca2+ entry, the resulting changes in intracellular Ca2+ levels could mediate the effects of the hormones on secretion.",
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