Wiktionary
n. (context biochemistry English) Any substance used to transmit a signal within a cell, especially one which triggers a cascade of events by activating cellular components
Usage examples of "second messenger".
The second messenger had arrived just four days ago, reporting that General Batu was riding to Tai Tung with a Tuigan delegation and a peace proposal.
I sent a second messenger to militia headquarters requesting reinforcements.
The second messenger added that the Royal troops of Hos-Harphax were coming up and seemed to regard this as good news, but then he spoke with a Harphax City accent.
In a luminous arc, not three yards distant, spun a second Messenger—.
A second messenger entered the room, glanced askance at the first.
Lord Jidu almost struck the second messenger, who arrived panting to report that shortly the crops would be ablaze beyond hope of salvage - unless the Acoma force could be neutralized to allow water brigades access to the river.
Lord Jidualmost struck the second messenger, who arrived panting to reportthat shortly the crops would be ablaze beyond hope of salvage unlessthe Acoma force could be neutralized to allow water brigadesaccess to the river.