The circulatory and metabolic effects in man of histamine, Mecholyl®, tetraethylammonium and atropine in the presence of circulating epinephrine and nor-epinephrine

In pheochromocytoma pharmacologic agents which provoke paroxysms of hypertension [i.e., histamine (1), methacholine chloride (2), and tetraethylammonium chloride (3)] have come to be widely employed as clinical diagnostic tools. Although the usual effects of these drugs, namely fall in blood pressure, tachycardia and vasodila-tation, are well recognized, the mechanism by which they induce hypertension in the pheo-chromocytoma patient remains unclarified. This study was designed to evaluate the circu-latory and metabolic responses induced by hista-mine, methacholine chloride (hereafter referred to as Mecholyl®) and tetraethylammonium chlo-ride (TEAC) in the presence of measured amounts of circulating epinephrine and nor-epinephrine. Atropine has been included as a test drug in an effort to determine the role which tachy-cardia may play in the observed responses, and also because Littman and co-workers (4, 5) have reported augmentation of nor-epinephrine's pres-sor effects by pretreatment with atropine. MATERIAL AND METHODS Blood pressure studies. Fifty-four convalescent hos-pital patients free of cardiovascular and renal disease were studied during a series of 82 infusion experiments. Twenty patients had paired infusions including both epinephrine and nor-epinephrine. 'This work was supported in part by grants from th