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Vasopressin enhances a calcium current in human ACTH‐secreting pituitary adenoma cells
Author(s) -
Mollard Patrice,
Vacher Pierre,
Rogawski Michael A.,
Dufy Bernard
Publication year - 1988
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2.13.2844618
Subject(s) - corticotropic cell , vasopressin , endocrinology , medicine , secretagogue , hyperpolarization (physics) , adenoma , current clamp , voltage clamp , patch clamp , chemistry , anterior pituitary , biology , electrophysiology , stimulation , hormone , organic chemistry , nuclear magnetic resonance spectroscopy
Arginine vasopressin (AVP) is a potent secretagogue for adrenocorticotropin (ACTH) release from normal corticotropes and from ACTH‐secreting pituitary adenoma cells. To explore the mechanism underlying this action, we investigated the effects of AVP on Ca 2+ ‐dependent action potentials and Ca 2+ currents in cultured human ACTH‐containing pituitary tumor cells (hACTH adenoma cells). Pituitary adenoma fragments removed at surgery from two patients with Cushing's disease were dispersed, and the isolated cells were grown in monolayer culture. Most of the cells showed ACTH immunoreactivity that persisted even after as much as 2 months in culture. Current clamp and voltage clamp recordings were carried out using the patch‐clamp technique in the whole cell configuration. AVP produced an increase in the amplitude and duration of action potentials in these cells, and substantially enhanced the transient after‐hyperpolarization after each spike. Under voltage clamp, hACTH adenoma cells showed two Ca 2+ current components: a low‐threshold, rapidly inactivating (T‐type) current; and a higher threshold, slowly inactivating (L‐type) current. AVP markedly increased the amplitude of the L‐type current without affecting the T‐type current. These data suggest that AVP may enhance Ca 2+ entry associated with action potentials by potentiating the activity of L‐type Ca 2+ channels. The resulting rise in cytosolic free Ca 2+ may be a key link in the process by which AVP stimulates ACTH release in the pituitary.— M ollard , P.; V acher , P.; R ogawski , M. A.; D ufy , B. Vasopressin enhances a calcium current in human ACTH‐secreting pituitary adenoma cells. FASEB J. 2: 2907‐2912; 1988.