Mechanism of beta-mercaptoethylamine-induced hypotension in the dog

¹ Pharmacology Section, Walter Reed Army Institute of Research, Walter Reed Army Medical Center, Washington, D. C.

Radioprotectant doses of beta-mercaptoethylamine (MEA) are toxic to the dog, inducing hypotension and hemoconcentration. Antihistaminics and two adrenergic blocking agents with antihistaminic properties were effective against MEA-induced hypotension. Adrenergic blocking agents with little antihistaminic action were ineffective against the hypotension. Antihistaminic compounds blocked MEA-induced hemoconcentration caused by a loss of plasma from the circulation, a portion of which may be found in the peritoneal cavity. Loss of plasma from the circulation and appearance of fluid in the peritoneal cavity is partially prevented by antihistaminics. MEA causes dermal whealing similar to that produced by histamine, and this whealing is prevented by intravenously administered pyrilamine maleate. These findings are interpreted as meaning that histamine release plays an important role in MEA-induced toxicity.