EFFECT OF GALANIN ON GROWTH-HORMONE (GH) RESPONSE TO THYROTROPIN-RELEASING-HORMONE OF RAT PITUITARY GH-SECRETING ADENOMATOUS CELLS (GH(1)) IN CULTURE

The growth hormone (GH) releasing effect of thyrotropin-releasing horm one (TRH) and galanin, a 29-amino acid peptide widely distributed in m ammalian CNS, alone or in combination was investigated in cultured rat pituitary tumor cells (GH(1)). TRH stimulated GH secretion in GH(1) c ells (maximal stimulation at the dose of 0.1 mu M). Galanin alone had a significant GH inhibitory effect in GH(1) cells at all the doses use d. When the two peptides were administered in combination, no signific ant changes as compared to baseline levels were observed. The results of this study indicate that galanin has potent direct inhibitory effec ts on baseline and TRH-stimulated GH release from rat tumor cells.