Histamine lipolysis I: changes in the free fatty acid levels of dog plasma after intravenous infusion of histamine.

The effects of histamine (Hi) and related compounds on free fatty acid (FFA) levels and % changes in FFA composition of dog plasma were studied after intravenous infusion. Hi at doses of 2-10 micrograms/kg while affecting no changes in the cardiovascular system elicited a dose-related increase in FFA levels in plasma, as did epinephrine. Though all of the FFA concentrations in plasma were increased by Hi infusion, % change of each FFA in the composition did not correspond to that of plasma concentration; % increases in palmitoleic acid, linolenic acid and linoleic acid were remarkable, while stearic acid (18:0) was lowest. The increase in arachidonic acid was not marked, but a dose-related increase was observed after Hi infusion. The H2-agonist 4-methylHi produced an increase in FFA levels, whereas the H1-agonist 2-methylHi was not effective. 4-MethylHi increased all of the plasma FFA levels and the relative changes were similar to those caused by Hi. The effect induced by Hi was blocked by the H2-antagonists cimetidine and ranitidine. Pretreatment with aminophylline potentiated the Hi effect, indicating that Hi lipolysis may be intimately related to cyclic AMP.