A specific G(0) heterotrimer couples somatostatin receptors to voltage-gated calcium channels in RINm5F cells

The peptide hormone somatostatin inhibits glucose-induced insulin secretion in the rat insulinoma RINm5F cells by inhibition of voltage-gated calcium channels. Here we used microinjection of antisense oligonucleotides directed against subtypes of G-protein subunits to determine the subunit composition involved in somatostatin-induced inhibition of voltage-gated calcium channels in RINmF5 cells, Injection of antisense oligonucleotides annealing to the respective mRNA of G alpha(o2), G beta(1) and G gamma(3) reduced the somatostatin-induced inhibition of calcium channels in these cells. Injection of antisense oligonucleotides directed against other G-protein subunits did not, suggesting that in RINm5F cells the somatostatin receptor couples to a G protein of G alpha(o2)beta(1) gamma(3) composition. By using a selective agonist of type 2 somatostatin receptors (SSTR 2) NC 8-12, we identified this receptor as the subtype coupling to calcium channels in RINm5F cells.