Effect of ACTH on VIP and Galanin Release from the Pituitary*

Abstract

The effect of adrenocorticotropin (ACTH) on the release of four regulatory peptides from the anterior pituitary of male rats has been studied using an in vitro perfusion system. Quartered anterior pituitaries from male adult Wistar rats were perfused with buffer containing different concentrations of ACTH and, subsequently, 56 mM KCl. Fractions of 1.5 ml were collected at 3 min intervals and analyzed for vasoactive intestinal peptide (VIP), galanin, 7B2, and substance P, using specific radioimmunoassays. Concentrations of 0.02, 0.1, 0.2, and 0.4 microM ACTH produced increases of 117 +/- 50%, 155 +/- 90%, 163 +/- 14%, and 161 +/- 3% (mean + SE), respectively, of basal release of VIP (P less than 0.001). However, concentrations of 1 microM and 2 microM ACTH suppressed VIP release to 74 +/- 6% and 47 +/- 4%, respectively, compared to basal release (P less than 0.001). Results for galanin release were similar: concentrations of 0.02, 0.1, 0.2, and 0.4 microM ACTH increased galanin release to 129 +/- 4%, 136 +/- 8%, 143 +/- 9%, and 133 +/- 9% of basal release (P less than 0.001) and 1 and 2 microM ACTH provoked a suppression of 52 +/- 7% and 50 +/- 13%, respectively, compared with basal release (P less than 0.001). Doses of ACTH that altered the secretion of VIP and galanin had no effect on 7B2 and substance P release. These results demonstrate that ACTH causes a release of pituitary VIP and galanin in vitro and, moreover, that this is a biphasic phenomenon.

Neuropeptides in anterior pituitary development

“…Studies on female rats with an altered galanin gene have confirmed that proliferation of lactotrophs under a high dose of oestrogen can be completely abolished (Wynick et al, 1998b), but galanin has also been associated with many other pituitary functions, such as the release of GH or LH, FSH and ACTH in humans. For further reading, we recommend the following references (Vrontakis et al, 1989(Vrontakis et al, , 1996Gabriel et al, 1989Gabriel et al, , 1990Calvo et al, 1990;Hooi et al, 1990aHooi et al, , 1997O'Halloran et al, 1991;Hyde and Howard, 1992;Niimi et al, 1993;Moore et al, 1994;Giustina et al, 1994;Hyde et al, 1996Hyde et al, , 1998Sauer-Ramirez et al, 1996;Hammond et al, 1997;Ceresini et al, 1997;Cai et al, 1998;Todd et al, 1998;Baranowska et al, 1999;Ren et al, 1999;Shen et al, 1999;Zdrojewicz and Sowinska, 2000;Elsaesser, 2001). This is in agreement with the presence of galanin in all pituitary cells during development; they all express galanin which, in the adult, may potentially activate specific functions in specific endocrine cells of the pituitary.…”

Galanin in human pituitary adenomas: frequency and clinical significance

“…However, it has previously been reported that the secretion of both GAL and ACTH from human ACTH‐secreting tumours in culture is stimulated dose‐dependently by corticotropin releasing hormone (Invitti et al. , 1999) and ACTH has been shown to stimulate GAL release from rat pituitary in vitro (Calvo et al. , 1990).…”

The cell blot assay in analysis of rat anterior pituitary cell secretion

“…After I h the medium was replaced by one containing TRH at concentrations of 1 • 10 -5 M, i X 10 -7 M or 1 x 10 -9 M. (Ottlecz et al, 1988;Koshiyama et al, 1987Koshiyama et al, , 1990 Cells were cultured overnight then incubated on the membrane in the presence of I x 10 -6 M galanin. (Calvo et al, 1990) Cells from male rats were cultured overnight then incubated on the membrane in graded concentrations (2 x 10 -sM, 2 x 10 -TM, 4 x 10 -7M, lX 10 -~ of ACTH.…”