Catecholamines in arteries and veins of the foreleg of the dog.

The catecholamine content of various blood vessels of the foreleg of the dog was measured by a fluorimetric method (48 vascular segments from 11 dogs) and also by bioassay (33 segments from 8 dogs). The results obtained by the fluorimetric method indicate that the average concentration of catecholamines in the brachial artery (0.14 /ig/g of wet tissue) was significantly lower than that in the ulnar (0.70 fjbg/g) and metacarpal arteries (0.66 fJLg/g); the average concentration in the brachial vein (0.17 fig/g) was significantly lower than that in the cephalic (1.30 fig/g) and metacarpal veins (0.47 /xg/g). The values obtained by bioassay were generally higher than those obtained by the fluorimetric method, but the differences between the arterial segments and between the venous segments were similar by both methods. There was a close correlation between the concentration of catecholamines in the different vascular segments and the relative responsiveness of these segments to nerve stimulation as reported previously (Circulation Res. 18: 263, 1966). Pretreatment with reserpine decreased markedly the catecholamines in segments of ulnar artery and cephalic vein. Intravenous infusion of norepinephrine in amounts sufficient to raise blood levels of catecholamines fiveto tenfold did not alter the content of segments of ulnar artery. ADDITIONAL