Expression of melanin-concentrating hormone receptors in insulin-producingcells: MCH stimulates insulin release in RINm5F and CRI-G1 cell-lines

Melanin-concentrating hormone (MCH) is a hypothalamic orexigenic peptide. R ecently, an orphan G-protein-coupled receptor (SLC-1) was identified that b inds RICH with high affinity. Here, we demonstrate the mRNA expression of t his receptor in insulin-producing cells Including CRI-G1 and RINm5F cells, and in rat islets of Langerhans. Immunofluorescence studies in CRI-G1 and R INm5F cell-lines demonstrated cell-surface expression of the receptor. Rat MCH significantly stimulated insulin secretion in both cell-lines, The pote ncy and the efficacy of RICH were significantly increased in the simultaneo us presence of forskolin, suggesting that MCH may amplify the insulinotropi c effect of cyclic AMP elevating stimuli. Salmon RICH, which differs from r at/human MCH by six amino acids, was less efficacious than rat/human RICH i n stimulating insulin release. The data provide evidence for the expression of MCH receptors in insulin producing cells. The insulinotropic effect of RICH may contribute to the regulation of metabolism and energy balance by t his peptide, (C) 2000 Academic Press.