The immunologic patterns of 3 human
pituitary adenomas of
Cushing's disease have been studied after gel exclusion chromatography (Sephadex G-50). The immunologic characteristics were examined with three radioimmunoassays specific for human
corticotropin (
ACTH),
lipotropin (LPH) and
beta-endorphin (beta-End). In cell
tumor extracts, chromatographic peaks corresponding to
beta-LPH,
gamma-LPH, beta-End and
ACTH were identified. The
ACTH/beta-LP-beta-End ratio was 1 in the 3 cases. Additionally, in the 3 cases, a chromatographic peak, partially cross-reacting in the beta-End assay, was eluted after beta-End, thus suggesting the presence of a fragment of the molecule. In 1 case, a peak of large molecular weight material with N- and C-terminal
beta-LPH and
ACTH immunoreactivity was observed, which corresponded to the precursor material. The release and the effects of various stimuli were studied on dispersed
tumor cells in primary culture. The
tumor cells had a biphasic basal secretion rate with a rapid increase of
ACTH/
beta-LPH-beta-End in the culture medium during the first 2 h. Then the release, studied during 2 days, was slower. Chromatographic studies showed that the
beta-LPH/beta-End ratio was 0.8 in the cells and 0.3 in the medium, due essentially to the release of beta-End and beta-End-like materials. The cells released
ACTH and
beta-LPH-beta-End in equimolar ratio after stimulation with
arginine vasopressin (AVP). The maximum effect was obtained with 10(-6) M AVP (D50 = 1 10(-9) M).
Dibutyryl cyclic AMP (2. 10(-3) M) induced maximal release of
ACTH/
beta-LPH-beta-End. This stimulation was suppressed by a 48-hour preincubation with
dexamethasone (10(-8)-10(-6) M). There was no effect of TRH and
LH-RH on cell release.
Dopamine (10(-6) M) specifically blocked the release of
ACTH/
beta-LPH-beta-End in 1 case. These data showed (a) heterogeneity of chromatographic profiles from case to case; (b) the presence of material in the
tumor,
cell extracts and culture medium corresponding to fragment(s) of beta-End; (c) culture studies demonstrated that
tumor cells remain responsive to AVP stimulation and
dexamethasone suppression, and (d) the
dopamine inhibition of
ACTH and beta-End release needs further investigation.