Anti-shock effect of ACTH: haematological changes and influence of splenectomy

ACTH-(1-24), injected i.v. into rats subjected to otherwise invariably fatal bleeding, at the dose of 160 micrograms/kg, causes a prompt and sustained increase in mean arterial and pulse pressure, with survival of all treated animals, at least for the first 2 hr. This is associated with a 100% increase in the volume of circulating blood, which is of normal composition, so that also the number of circulating red cells is doubled as compared to controls. Splenectomy greatly impairs the beneficial effect of ACTH on blood pressure, blood volume and survival. It is concluded that, in cases of acute hypovolemia, ACTH-(1-24) induces a recall of blood from storage sites and its redistribution, though the precise mechanism is as yet unknown.