Galanin is released by adrenocorticotropin-secreting pituitary adenomas invivo and in vitro

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).