Galanin, a brain-gut peptide, is also synthesized and released by the pitui
tary. In man, galanin-like immunoreactivity and galanin messenger RNA have
been detected specifically in normal and tumoral corticotropes, but little
is known about the production and release of galanin by the human pituitary
. We evaluated galanin release by 5 ACTH-secreting pituitary adenomas in cu
lture and plasma galanin concentrations in the inferior petrosal sinuses (I
PSs) of 15 patients with Gushing's disease before and after CRH administrat
ion. For comparison, the galanin response bo CRH was evaluated in 8 normal
controls.
Galanin secretion by pituitary tumor cultures ranged from 30-230 pmol/4 h.
Incubation with CRH induced an increase in galanin concentrations (100 pM C
RH: 151 +/- 32%; 1 nM CRH: 232 +/- 43%; 10 nM CRH: 246 +/- 35%; and 100 nM
CRH: 270 +/- 44% unstimulated levels at 24 h, P < 0.05). The stimulatory ef
fect of CRH seemed to be dose-dependent. Basal and CRH-stimulated ACTH and
galanin concentrations also exhibited a strong positive correlation in sing
le tumor cultures.
At IFS sampling, mean basal plasma galanin concentrations in the dominant I
FS were somewhat higher than those registered at the periphery (18.6 +/- 1.
94 vs. 15.8 +/- 1.60 pmol/L, P = 0.05). Administration of CRH induced a mod
est but significant increase in galanin concentrations at all three samplin
g sites. No correlations were found between ACTH and galanin levels in the
IPSs and at the periphery. Different from what was observed in patients wit
h Gushing's disease, CRH did not modify plasma galanin concentrations in no
rmal subjects.
In conclusion, this study demonstrates that galanin is released by human tu
moral corticotropes and responds to CRH. The role of locally produced galan
in is, as yet, unknown but may possibly be that of a autocrine/paracrine mo
dulator. (J Clin Endocrinol Metab 84: 1351-1356, 1999).