Effects of norepinephrine on transmembrane calcium transport in rat mast cells

The effect of norepinephrine on transmembrane passage of calcium in rat peritoneal mast cells, was studied in an in vitro system. It was found the histamine release from mast cells induced by the ionophore A 23 187 in normal calcium medium and compound 48/80 in a calcium-free medium was suppressed by 10(-3) M norepinephrine but not at concentrations in the range 10(-5)-10(-4) M. When the secretory process is totally dependent on the presence of calcium in the incubation medium, i.e. calcium-depleted cells, 10(-5) M norepinephrine suppresses the histamine release induced by low concentrations of compound 48/80. The effect of norepinephrine (10(-5) M) on strontium-induced "spontaneous' histamine release was also studied. It was found that norepinephrine (10(-5) M) totally inhibits the progressive histamine release induced by strontium. It is possible to evoke secretion in a calcium-free medium, and subsequent introduction of Ca2+ will result in optimal histamine release. This demonstrates a secretory process in which we can distinguish between utilization of endogenous versus exogenous calcium. The release that is dependent on extracellular calcium is inhibited by norepinephrine (10(-5) M). These data indicate that the suppressive effect of norepinephrine (concentrations less than 10(-3) M) on histamine release from rat mast cells is due to an interference in transmembrane passage of calcium.