NO synthase activity does not influence electrical activity of mouse pancreatic B-cells

The membrane potential of mouse pancreatic B-cells was recorded with intracellular microelectrodes. At a low concentration the NO synthase inhibitor N omega-nitro-L-arginine methyl ester (L-NAME, 100 mumol/l) did not alter electrical activity induced by 15 mmol/l glucose. At 5 mmol/l L-NAME depolarized B-cells similarly to L-arginine. The depolarization of the B-cell membrane induced by 5 mmol/l L-arginine in the presence of 15 mmol/l glucose was not inhibited but further increased by the addition of 15 mmol/l L-NAME. D-arginine which is not used as a substrate by the NO synthase also depolarized the B-cells. However, higher concentrations were necessary than for L-arginine pointing to a preferential transport of the L-enantiomer. It is concluded that the electrical activity of pancreatic B-cells is not influenced by the NO synthase and that the enzyme is not involved in the arginine-induced depolarization of B-cells.