Effect of amylin on prolactin release.

OBJECTIVE Amylin is a 37-amino acid peptide that is secreted from the pancreatic beta cells. This peptide is cosecreted with insulin from the pancreas by glucose. Amylin plays a role in glucose homeostasis and in the regulation of lipid metabolism. Amylin receptors were identified in central nervous system of rats. There is no available data on the effects of amylin on the pituitary hormones secretion. The aim of this study was to evaluate the effect of amylin on prolactin release in vivo and in vitro experiments in male adult Wistar Kyoto rats. METHODS Amylin in a dose of 1 microg/5 microl was injected intraventricularly (i.c.v) during 5 min. using automatic pump. The control group received 5 microl cerebrospinal fluid. Amylin was injected intravenously (i.v) in a dose of 10 microg in 300 microl 0.9% NaCl. The control group received 300 microl 0.9% NaCl. In vitro experiment was performed in the pituitary cells culture conditions. Amylin was added to pituitary cell culture in a dose of 1, 10, 100 nM. Prolactin concentrations were determined using RIA methods. RESULTS Central or peripheral administration of amylin caused a significant decrease of serum PRL concentrations as compared with control after 120 min. After 240 minute incubation of the pituitary cells culture with amylin in doses of 10 nM and 100 nM a significant inhibition of the release of PRL was found. However we found that the effect of amylin on the release of PRL depended on dose and time of incubation. A significant increase of PRL level was observed in cultured media in the presence of 1 nM of amylin after 60 min. CONCLUSION Our results indicate that amylin administrated centrally and peripherally as well in the cell culture inhibits PRL release.