Abstract
Horseradish peroxidase (HRP) given intravenously was shown to possess a marked hypotensive effect in cats. The effect was not noticeably influenced by antihistamines. Indomethacin and acetylsalicylic acid completely blocked the hypotensive effect of HRP. It is concluded that the effect of HRP on blood pressure is due to stimulation of the synthesis of metabolites of arachidonic acid.