Adrenocorticotropin and Lipotropin Secretion by Dispersed Cell Cultures of a Human Corticotropic Adenoma: Effect of Hypothalamic Extract, Arginine Vasopressin, Hydrocortisone, and Serotonin*

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Abstract
Basal and modulated secretion of ACTH and lipotropin (LPH) by cultures of trypsin-dispersed cells of a biopsy of a human corticotropic adenoma have been examined. ACTH secretion was detectable throughout the period of culture (13 days) but declined steadily from an initial production rate of 238 ± 124 ng/3 × 105 cells/12 h. The time course of secretion showed a slower phase over the first 4 h, with increases up to 12 h. An extract of rat stalk median eminence caused a significant (P < 0.005) dose-dependent increase in both ACTH and LPH secretion during 30 min. The patterns of response for ACTH and LPH were very similar; both exhibited a decline in the basal release of peptide subsequent to the period of stimulation. The addition of hydrocortisone (0.2 μg/ml) did not suppress basal ACTH secretion during 30 min but significantly (P < 0.05) inhibited stimulation produced by rat stalk median eminence extract. Arginine vasopressin (dose range, 1-9 ng/ml) significantly (P < 0.025) stimulated both ACTH and LPH secretion during 30 min. The patterns of response were again very similar. Serotonin (dose range, 0.01-10 μg/ml) did not affect ACTH secretion during incubations of 30 min to 4 h. The results obtained with the cell cultures of a human corti-cotropic cell adenoma concur with in vivo findings of incomplete autonomy of secretion, parallel secretion of ACTH and LPH in response to provocative stimuli, and suppression by corticoste-roids. The technique has potential for exploring the cellular mechanisms controlling secretion by human corticotropic adenomas as well as the nature of the hormones produced.