Calcium mechanism of norepinephrine activation of ionic pump in somatic cells of lumbricus terrestris earthworm muscle wall.

摘要

Blockade of norepinephrine-induced hyperpolarization in earthworm muscle cells was observed in a calcium-free medium, after substitution of Ca(2+)with Mn(2+), and in the presence of verapamil or chlorpromazine to the incubation saline. Changes in Ca(2+)concentration in the saline and addition of caffeine had no effect on the resting potential of muscle cells. It was hypothesized that signal transduction from norepinephrine-activated membrane adrenoceptors to the ionic pump in earthworm muscle cells depends on influx of extracellular Ca(2+)and subsequent involvement of Ca(2+)-accepting proteins similar to calmodulin in vertebrates.