¹ Department of Medicine, Wayne State University College of Medicine, Detroit, Michigan

The factors affecting myocardial storage and release of catecholamines were investi gated. The catecholainine concentration of heart muscle of normal dogs averaged 0.617 g. per Gm. of heart muscle. Ventricular tachycardia, fibrillation, and reserpine caused a slight reduction in myocardial catechol amine concentration, while nicotine resulted in a slight increase. Iproniazid was without effect. The injection of the amino acid, Dopa, and of the combinatiou of Dopa and iproni azid, resulted in a significant elevation of catecholamines in heart muscle.

In animals pretreated with Dopa and iproniazid, nicotine caused a significant in crease in myocardial catecholaniines. It is likely that stimulation of the adrenal medulla and sympathetic nerve endings by nicotine elevated catecholamine levels in blood, with subsequent storage in the heart and other organs.