Evidence for a histaminergic mechanism on the effects of angiotensin II in the rabbit aorta and rat lung.

The influence of a histidine decarboxylase (HD) inhibitor, GYKI 11.121, on the action of angiotension II (AII) was investigated in the isolated continuously superfused rabbit aortic strip and perfused rat lung. An A II analog, Sar1-Ile5-A II, was also used only in aortic strip experiments. The myotropic effects of both peptides on the rabbit aorta were found to be inhibited when GYKI 11.121 was added to the superfusion medium. However, the vasoconstrictor effect of A II was found to be enhanced in the isolated rat lung following the addition of GYKI 11.121 to the perfusion medium. These findings are explained by the presence of a histaminergic component in the myotropic action of A II peptides.